This articles examines different theories of suicide, starting with a review of two major sociological theories, those of Durkheim & Henry & Short. The discussion then turns to individual theories of suicidal behaviours, classified into 3 major types: physiological, intrapsychic, & interpersonal. Intrapsychic theories are further divided into psychoanalytic theory, social learning, & cognitive process. Social networks & the family are examined in interpersonal theories. The article concludes with a discussion of why theories of suicide are important in clinical suicidology. (27 refs.)