Recurrent acute otitis media (RAOM) and chronic otitis media with effusion (COME) exhibit familial aggregation, but environmental risk factors (day care attendance, cigarette smoke exposure, and bottle feeding) are also important in their development. The Family Study of OM was designed to ascertain the RAOM/COME status of families whose children participated in Otitis Media Research Center studies between 1978 and 1984. Probands were treated with tympanostomy tubes, and had their RAOM/COME status ascertained as criteria for entry into these studies. For the Family Study of OM parents were interviewed about their otitis media and risk factor history; mothers were interviewed about their children's history, and pertinent medical records were obtained. Members of 173 families were examined with otomicroscopy and multifrequency tympanometry; 19% of parents and 32% of siblings were classified as affected, which is substantially higher than RAOM/COME rates from previous reports. Risk factor profiles differed significantly (P < .001) between parents and their children. Younger generation (adjusted odds ratio [OR] = 4.18, 95% confidence interval [Cl], 2.74, 6.36), day care attendance (OR = 1.96, 95% Cl, 1.32, 2.91) and male gender (OR = 1.42, 95% Cl, 1.03, 1.97) were significantly related to RAOM/COME using logistic regression. Analyses confirm (1) higher disease rates in families with an affected member compared to existing studies of the general population, (2) increased risk of RAOM/COME associated with known risk factors, and (3) increased risk for parents irrespective of risk factors. Additional analyses will explore competing models of disease susceptibility using genetic models and known risk factors. © 1996 Wiley-Liss, Inc.