A frame of reference for studying human disease is presented. An individual's social behavior serves as the orienting theme. Special forms of social behavior are in effect what tie an individual to his physical and social space, and alterations here can lead to disease. Causes of disease can thus be linked to behaviors of the individual. Although associated with basic changes in the psysiologies and chemistries of the individual, disease invariably comes to affect the individual's behavior and adaptation. Different ways in which such behavioral changes can be conceptualized are discussed. The individual relies on these behavioral changes as the data for evaluating his disease and deciding about medical treatment. A model of how an individual processes information about illness and makes decisions designed to alleviate his condition is presented. Finally, the rationale and value of keeping behavior and adaptation in mind when studying disease are discussed.