The present longitudinal study was designed to determine the prevalence of depression in male and female patients undergoing cardiac surgery, and to examine what factors are associated with depression before and after surgery. One day prior to surgery (T1), and one day prior to discharge from the hospital (T2), 141 patients completed a psychometric test battery including the Center for Epidemiological Studies Depression Scale (CES-D), the State-Trait Anxiety Inventory (STAI), and the Perceived Social Support Scale (PSSS). Data were also collected on 13 physiological measures. Forty-seven per cent of patients were depressed (defined as a score of 16 or above on the CES-D) at T1. Scores on the CES-D significantly increased from T1 (M = 15) to T2 (M = 20), with 61 per cent of patients classified as depressed at T2. Factors associated with depression at T1 were female gender, higher state anxiety, and less social support. Depressed patients at T2 were characterized by higher scores on the STAI at T2 and higher scores on the CES-D at T1. The prevalence of depression in cardiac surgery patients, particularly women, may be underrecognized and warrants increased attention.