We conducted a prospective cross-sectional epidemiologic study of conjunctivitis-otitis syndrome during two 3-week periods of consecutive winters. A representative sample of 184 pediatricians and ear, nose and throat specialists in the Paris area recruited 2901 children from 6 to 36 months of age presenting with acute otitis media, of whom 465 (16%) also had purulent conjunctivitis. In sampled children, the culture of the conjunctival exudate yielded bacterial pathogens in 419 patients: Haemophilus influenzae, 371 (89%); Streptococcus pneumoniae, 72 (17%); and Branhamella catarrhalis, 23 (5%). Pulsed field gel electrophoresis analysis of paired H. influenzae isolates from the conjunctival exudate and middle ear fluid of 21 patients showed identical strains in each patient.