- Background: Given the relatively high prevalence of recurrent and persistent acute otitis media (AOM) and the prominent etiologic role of Streptococcus pneumoniae, especially penicillin-nonsusceptible strains in children with these conditions, new alternative treatments are desirable. Methods: Children 6 months–4 years of age with AOM considered to be at risk for recurrent or persistent infection received large dosage cefdinir 25 mg/kg oral suspension once daily for 10 days. Children were evaluated pretreatment (day 1), on therapy (days 4–6), end of therapy (days 12–14) and at follow-up (days 25–28). All children had tympanocentesis at enrollment. In culture-positive children, tympanocentesis was repeated after 3–5 days (days 4–6) unless evidence of absence of middle ear effusion was documented. Results: Of 447 children enrolled, 230 were clinically and bacteriologically evaluable (74% 2 years old or younger; 57% treated for AOM in previous 3 months). Bacteriologic eradication, based on repeat tympanocentesis on days 4–6, was achieved in 74% (170 of 230) of children; 76% (201 of 266) of AOM pathogens were eradicated. Eradication of penicillin-susceptible, -intermediate and -resistant S. pneumoniae was 91% (50 of 55), 67% (18 of 27) and 43% (10 of 23), respectively (P < 0.001); eradication of H. influenzae was 72% (90 of 125). Overall clinical response at days 12–14 was 83% (76 and 82% for children with S. pneumoniae and Haemophilus influenzae, respectively). Sustained clinical response at days 25–28 was 85%. Clinical response was 83% for culture-positive children versus 96% for culture-negative children at baseline tympanocentesis (P < 0.001). Conclusions: In this study of AOM among children at risk for persistent or recurrent infection, large dose cefdinir resulted in an overall successful clinical response at end of treatment of 83%. This regimen was efficacious against penicillin-susceptible S. pneumoniae, but effectiveness was markedly decreased against nonsusceptible strains and was moderate for H. influenzae strains.