This paper examines the social construction of diagnosis and illness in several ways. First, I discuss the centrality of social construction in medical sociology. Next I discuss the major role of diagnosis in social construction, leading to the need for a sociology of diagnosis. I emphasize controversial and conflictual diagnoses, as a first step toward a more general sociology of diagnosis. Then I put forth a typology of social construction, involving four combinations based on whether a condition is generally accepted and whether a biomedical definition is applied. Next I detail a series of stages in the social construction of a condition. In that process, my primary concern is the initial social discovery, which is essentially a matter of diagnosis, with a secondary emphasis on illness experience. This is followed by stages of treatment and outcome, which recursively affect social construction. I conclude by noting the health policy implications of the social constructionist perspective.