This study investigated women's experiences with the long-acting, injectable contraceptive Depo-Provera. Fourteen women were interviewed and 57 charts of clients at a Canadian Sexual Health Centre were reviewed to generate a theory of use. A three-stage process model describes women's choice of this contraceptive and decision to continue or discontinue use. This model suggests that women's use of Depo-Provera is determined by a complex interaction of individual cognition, relational processes, and sociocultural contexts.