An understanding of community perceptions of illness, especially disease definitions that are unique to a particular culture, is essential for developing culturally appropriate primary health care programs. Malaria is endemic in the Ibarapa District of Oyo State, Nigeria, and one of its major complications, febrile convulsions, affects nearly one-third of preschool children at least once in their lifetime. Perceptions among the local Yoruba people categorize malaria and convulsions as part of two different disease processes. Ideas of causation, severity, seasonality, and treatment are in many ways opposites. This means that parents do not perceive the dangers of convulsions when their children suffer malaria. Unfortunately the small children themselves cannot be part of the decision-making process which involves potentially toxic treatment practices. Based on an understanding of Yoruba beliefs, primary health care and health education interventions have been designed that encourage parents to take prompt action when they recognize that their child has malaria.