5. It's been awfully quiet upstairs. When you go up, you find your 5-year-old and his kindergarten pal with their clothes off, examining each other. You:

A. Tell them they need to have their clothes on for snacks downstairs.
B. Take the other kid home immediately, then give your son a time-out.
C. Apologize for barging in and close the door so they can have privacy.

Answer: A. If you make a big scene, you'll just scare the kids. But unless you're comfortable with the idea of your child playing these types of games until he satisfies his curiosity, you should probably step in and redirect him and his friend to another activity (snacks are always a good diversion).

"Children like to check out other kids' bodies," says Ladd. "You can't fault them for being curious, but you need to explain why bodies are private."

When you're all downstairs eating pretzels, tell them it's okay to be curious but on playdates they should keep their clothes on, say experts. Later, when your child's buddy has left, you can elaborate. This would be a good opportunity to tell him what's okay touching -- hugging your family and friends -- and what's not #151; touching other people's genitals or letting people touch his.

If he's still interested in what bodies look like, you can get him an age-appropriate book. (For some good choices, see "Books for All Ages.")

Be sure to call the other child's parents and tell them what the kids were up to so they can have their own discussion. It's also wise for you and your mate to get in sync, says Martin. "Parents should talk to each other about how they want to talk to their kids about sex," she says. "That way, they can be consistent."