Playing doctor is totally harmless, and is a natural act for children to explore their own, and the other gender's body. At the average age when this happens, they are not even able to imagine what they are supposed to 'do', let alone actually act on it.
I once heard a story of a little boy who had secretly seen his parents have sex, and of course tried to act it out with his neighbor girl. They lay on top of each other, shoved and moaned, but had NO idea why this was supposed to be pleasurable.
Until the age of 12, boys generally have no interest nor ability to seriously do anything sexual, girls are usually a little bit earlier.

There is absolutely nothing wrong with that, unless either the boy or girl doesn't want to 'play along' , and the other keeps on going. But even then I wouldn't call it harassment, but part of the learning process, and the boy/girl needs to be corrected (and explained to respect other peoples' non-interest).

Plus, don't we all like to play 'doctor' every now and then?? :)

Hmm...

Well, when I was five, I was the neighborhood chief of the medical staff.

There were some lilac bushes around the back, and somewhere, somehow, I got the idea of inviting other kids in the neighborhood into the lilac bushes... I think it started with me and another guy needing to pee, because I remember ducking into the bushes to pee, and I remember noticing with curiosity that his urine was a different concentration of yellow from mine, and then I remember noticing that he was not circumcized, and that got me really curious... and from there it led up to me organizing parties where, at its peak, there being five of us in the lilac bushes, three boys and two girls, and one moment in particular that firmly stands out was when I fingered Trudy and got my first sniff of something having a very different pH from what I already knew about.

It all came to a crashing end when some new people moved in next door... a dutch family - evidently very Calvinist - and they had two boys about my age (I remember how *blond* they were) and so I thought to welcome them to the neighborhood by wauy of introduction to my favorite sport, and they played along, but the older of the two, who was about seven I think, seemed a bit upset about it, and the next thing I knew there was a very angry dutch father pounding on my parent's door screaming something in broken english.

I got a talk from my parents about how the difference between humans and animals is that intelligence is greater than emotion, about how that enables language, and, with an illustrated anatomy text, why that leads to clothing...

It wasn't that profound of a lesson, because they already knew that I knew that humans were mammal and that there was such a thing as mating and birth, because dad took me hunting with him and would have me watch while he skinned and gutted the beasts, during which he would point out anatomical characteristics, plus mom would let me watch while she mated her show cats, and even woke me up one time so I could see them give birth, because I'd told her I wanted to watch, etc... so I think they figured I needed a topper on those extra duties and responsibilities expected as a consequence of being human.

However... me and one of the girls, Gail, sort of kept it going. Workers were doing street construction - paving all our roads that had been gravel - and so would leave pots of oil buring overnight in order to mark where construction was happening, so she and I played a fun little game of seeing who could put out those flames faster and more effectively... me with my ability to strike with tactical precision, or her with her ability to do wide area strageic bombardment.

Then the first grade happened, and my attention shifted to fretting about how much I hated school.

Did it hurt anything? I dunno. I do know that when we had to have full physicals, wherein the doctors had to pull down our underwear to check out the testicals, some of the guys in my grade would go spastic just about the part of peeling to their underwear - which to me was so ordinary I only considered it an accomodation to society to keep those on when sneaking out to play on sunny saturday mornings... plus when I was 12 there was a molester going through town, and he tried some stupid head-game trick of using my favorite soda-pop to get me into a public washroom, and I had him pegged so fast that not only was I on my bike ratting away from there faster than the Flash, but I made a point of spinning a skid to pepper him with as much gravel as I could (he got busted about six weeks later, after some of the guys in my age group had fallen for it and then broken down and talked to their parents or the church elders, which I thought was odd, because they were supposed to be the tough guys while I was the sixth grade pencil-neck science geek)... and then in junior-high, one sunny afternoon, puberty hit, and between the time I felt that first sledgehammer of hormones to the time I made it home for dinner I had my whole dating strategy for the rest of my teens worked out, such that for the rest of junior high and all through high school it was a straitforward process of working out tactical logistics while so many of my classmates seemed to exist in a perpetual state of angst.

So... did playing doctor cause any harm? I dunno... did it? I don't feel especially harmed.

There came a day when I had a kid of six, and he was caught in the bushes with a kid his age who's parents had immigrated from Peru, and the father was falling to pieces over it. I tried to help him relax, and over some double ryes I explained to him how, for mine, I talked about how the difference between humans and animals is that intelligence is greater than emotion, about how that enables language, and, with an illustrated anatomy text, why that leads to clothing...

not at all

Children playing doctor is fun for children, It show that children can be caring as well, we know that doctor help people who are sick and for children play as if they are doctors is a good sign, I would support my children playing doctor.

It is only natural for young children to become curious about their own bodies as well as the bodies of their friends, especially if they have friends of the opposite sex. Exploring eachothers anatomy can help young children learn firsthand about the differences between boys and girls, as well as the different structures of people's bodies. They will find that everyone is shaped and built a little differently, that some may be bigger, some smaller, some have light skin, some have dark skin, and that it's all normal. If you find your child and his/her friends playing doctor and exploring each other's bodies it is important not to overreact or shame the children. Rather you may want to talk about what they are playing, what they observed, and possibly the differences between boys and girls (use proper labeling such as "vagina" and "penis", not "wee-wee" or "pee-pee"). But do set some healthy limits, such as "Do not touch your friends private parts". To foster doctor play, you may want to provide actual doctor toys for pretend play. Children love giving each other shots and listening to another's heartbeat (or pretending to do so).