Risk factors associated with adult onset wheeze were examined in a case control study of subjects aged 39-45 yr derived from a community cohort of 2,056 asymptomatic children originally studied in 1964. Participants included 102 cases with adult onset wheeze (since age 15) and 217 controls with no wheeze. Logistic regression analysis was used to determine independent risk factors for wheeze among all cases and three subgroups: doctor diagnosed asthma (n = 24), wheeze with chronic cough and phlegm (n = 31), and other wheeze (n = 47). The risk of adult onset wheeze among all cases increased with low socioeconomic status (relative risk [RR] 2.36), current smoking (RR 2.01), positive atopic status (RR 3.28), and positive family history of atopic disease (RR 5.49). Gender was not related to the risk of wheezing. The pattern of significant independent risk factors differed between the subgroups of cases. Socioeconomic status was associated with cough and phlegm and other wheeze. Smoking habit was only related to cough and phlegm. Atopy was associated with doctor diagnosed asthma and cough and phlegm. Family history of atopic disease was related to all subgroups, suggesting that despite apparent heterogeneity in diagnostic labeling, concurrent symptoms, and other risk factors, the different forms of adult onset wheeze may share a common allergic basis.