This study explored the link between exposure to shiftwork and the prevalence of major depressive disorder (MDD) during and after the shiftwork experience. A geographically based random telephoning strategy was used to identify 98 current and former shift workers (31 women, 67 men, 40-65 years old, mean age 55.2 years). Each subject was then given, by telephone, two standardized psychiatric assessment instruments: the SCID to determine lifetime incidence of MDD; and the CES-D to evaluate current depressive symptoms. A modified version of the Standard Shiftwork Index (SSI) was also administered. In addition to confirming previous findings regarding the detrimental effects of shiftwork on sleep and social/domestic factors, there was an unexpectedly high prevalence of MDD identified, occurring during or after shiftwork, with a higher rate for women than for men. The study also provided suggestive evidence that increasing exposure to shiftwork (up to 20 years) was associated with an increased lifetime risk of MDD.