Nulliparous women, between 11 and 21 weeks gestation, were randomized to receive either placebo or 2,000 mg elemental calcium per day as subjects in the NIH-sponsored Calcium for Preeclampsia Prevention (CPEP) trial. Six weeks following delivery, a demographic and medical history questionnaire, and the Edinburgh Postnatal Depression Scale (EPDS), was mailed to subjects in two CPEP sites, Portland, OR and Albuquerque, NM. Subjects in the Portland site were reassessed at 12 weeks following birth. There were no statistically significant differences between treatment and placebo groups with respect to maternal demographics, history of prior depressive illness, impact of life stressors, utilization of breast-feeding, nor infant characteristics. Utilizing a standardized definition of depression (EPDS 14), chi square analysis of 293 women at 6 weeks postpartum indicated a trend (p = 0.07) toward less depression in calcium-supplemented women. Among the 247 women evaluated at 12 weeks postpartum, calcium-treated subjects had significantly less depression (p = 0.014).