To determine how frequently acute otitis media (AOM) occurs, we enrolled children between 6 months and 3 years of age who returned several weeks before and 6 to 10 times during a cold for tympanometry and photography of the tympanic membrane. American Academy of Pediatrics (AAP) criteria were used to diagnose AOM. Children visited their physicians at their discretion. AOM occurred in 17 (55%) of 31 colds; in 12 (100%) colds with pre-existing middle ear effusion (MEE); and in 5 (26%) of 19 colds with no pre-existing MEE (P < 0.0001). Four patients received antibiotics from their physicians. Of 17 children with AOM, 12 did not seek care. AOM is common during colds, particularly with pre-existing MEE.