Many different treatments have been suggested for the premenstrual syndrome (PMS), including such nutritional supplements as vitamins, minerals and essential fatty acids. There is little agreement about the causes or treatments of the syndrome. The effect of a nutritional supplement, at high and low dosage, on premenstrual symptoms was assessed in a double-blind, placebo-controlled study. Also, the nutritional state of 11 women with PMS was evaluated. There was laboratory evidence of significant deficiencies in vitamin B6 and magnesium; other deficiencies occurred frequently, also. The multivitamin/multimineral supplement was shown to correct some of these deficiencies and, at the appropriate dosage, to improve the symptoms of premenstrual tension.