Lack of compliance with medical therapy is a major clinical problem. We undertook a study to determine whether degree of acculturation to mainland U.S. culture was predictive of compliance in Puerto Rican families having a child with asthma. A questionnaire was administered to parents of Puerto Rican asthmatic children attending an asthma clinic and taking oral theophylline as part of their medical management. The questionnaire included items concerning medical, socioeconomic, and cultural variables, as well as a standardized instrument devised to measure degree of acculturation. Compliance was measured by a serum theophylline level obtained at the time of the visit. Families were divided into compliant (n = 15) and noncompliant (n = 13) groups based on their child's serum theophylline determination. There was a significant difference in mean acculturation scores between compliant and noncompliant groups (p = .008). Those in the complaint group had scores indicative of a style of acculturation that integrated aspects of both "Anglo" and Puerto Rican lifestyles. Those in the noncompliant group had scores indicative of a less acculturated lifestyle. The findings of this study show that degree of acculturation is a predictor of compliance with medical therapy in mainland Puerto Ricans. Additional studies with other cultural groups are needed, as well as other studies incorporating acculturation into a multivariate model of compliance.