Of 429 children with acute otitis media who returned for follow-up evaluation, 49 (11%) were unresponsive to a 10- to 14-day course of ampicillin, amoxicillin, or erythromycin/sulfisoxazole. Patients with persistent purulent otitis media were noted to have immobile, bulging, yellow or grey, abscessed tympanic membranes at the follow-up visit. A myringotomy was performed on 45 children. Cultures of middle-ear exudate yielded ampicillin-resistant Haemophilus influenzae in 14 (31%), ampicillin-susceptible pathogens (H. influenzae or Streptococcus pneumoniae) in 23 (51%), and no growth in 8 (18%).