An epidemiological study was conducted in order to monitor the involvement of penicillin-resistant pneumococci (PRP) in treatment failure in acute otitis media (AOM), in an area of France where resistance to antibiotics is high. A total of 293 children presenting to 12 ear, nose and throat (ENT) specialists were included in the study. The mean age of the patients was 15.3 months and most of the children (58.7%) were attending day care centres. Bacteriological sampling demonstrated that in 146 cases (49.8%), no pathogen was present at the time of treatment failure. In the remaining patients Streptococcus pneumoniae was the most frequently recovered pathogen, being isolated from 81/147 (55.1%) of bacteriologically documented cases. Serotype 23F was the predominant strain, representing 53% of all S. pneumoniae isolates recovered. Resistance or reduced susceptibility to the prescribed antibiotic was seen in 70/81 (86.4%) of the S. pneumoniae isolates. In 32 out of 49 children administered a beta-lactam antibiotic, treatment failure involved PRP. Amoxycillin seemed to be the most active oral beta-lactam against these pathogens. The multiresistance of S. pneumoniae poses a serious therapeutic problem and should make myringotomy and bacteriological sampling obligatory in cases of antibiotic treatment failure.