Children in day care, like their home-reared peers, frequently become ill. Whether they are sick more frequently than those not in day care has been a question difficult to resolve because of the problem of appropriate control studies. Many pediatricians are convinced that this is so. There are data that infections due to certain specific agents including hepatitis A, Haemophilus influenzae type B, and Giardia lamblia occur more often in day-care center attendees. Clinical entities such as diarrhea, meningitis, and otitis media have also been shown to be more common in day-care center attendees. A recent review in Pediatrics1 provides a good overview of the problem.