Although nasopharyngitis usually results from a viral infection, it is the leading cause of use of antimicrobials in pediatric patients. A study of the criteria used by pediatricians to prescribe antimicrobials in uncomplicated nasopharyngitis was undertaken. Each of 700 pediatricians enrolled ten consecutive patients with uncomplicated nasopharyngitis. Use of antimicrobials was left to the discretion of the physician. Antimicrobials were used in 59% of pediatric patients evaluated for nasopharyngitis. Criteria considered as the most important for deciding to use antimicrobials induced purulent secretions (87.2%), congestion of both tympanic membranes (82.8%), cough (79.2%), fever greater than 39 degrees C (77.2%), and a history of otitis media (69.8%). Data on the outcome was available for 69% of patients. Acute otitis media was the main complication, with a rate of 7.7%; this rate was lower in the treated group (5.4%) than in the untreated group (10.9%). A positive history for otitis media and the appearance of the eardrums at evaluation were the best predictors of otitis media.