OBJECTIVE: Scientific evidence suggests that cyclic fluctuations in a variety of nutrients, especially calcium, may help to explain some features of premenstrual syndrome (PMS). We determined the efficacy of calcium supplementation in women suffering from PMS. MATERIALS AND METHODS: A double-blind clinical trial was designed to evaluate the effect of calcium supplement therapy on PMS symptoms. The study groups were selected from young female college students, based on PMS criteria. The subjects were divided in two groups; one group received placebo and the other received 500 mg of calcium carbonate twice daily for 3 months. The severity and intensity of symptoms, including early fatigability, changes in appetite, and depression, were evaluated using a standard questionnaire. Symptoms were compared before and after treatment. RESULTS: The mean age was 21.4 +/- 3.6 years. Early tiredness, appetite changes, and depressive symptoms were significantly improved in the group receiving calcium treatment compared with the placebo group. CONCLUSION: Our results showed that calcium supplements reduced early fatigability, changes in appetite, and depression in women with PMS.