In an effort to determine if bacterial water quality was related to the incidence of otitis externa (swimmer's ear), a retrospective study was conducted from July, 1980 to September, 1980. Data from 29 cases and 29 controls matched for age and sex were collected. Warm air, warm water, age of less than 18 yr, swimming, and length of time spent swimming were associated positively with cases of otitis externa. Water quality, as measured by fecal coliforms, enterococci, and Pseudomonas aeruginosa was not found to be associated with otitis externa.