To assess the effectiveness of a vitamin/mineral supplement in controlling symptoms of premenstrual syndrome (PMS), we conducted a double-blind randomized study on 44 women with PMS. Subjects were carefully screened and excluded if underlying physical or psychopathological conditions were noted. Follicular and luteal testing with a menstrual symptom questionnaire, subdividing PMS into four subgroups, was completed for 1 month prior to treatment and for three menstrual cycles during treatment. Subjects were randomly assigned to receive either placebo or six or 12 tablets of the supplement a day for three menstrual cycles. All subjects had significant differences in severity of symptoms between the follicular and luteal phase of the control cycle. Comparing pre- vs posttreatment luteal phase scores, significant placebo effects were noted for two PMS subgroups. Significant treatment effects were noted in three subgroups for the six-tablet group and in all four subgroups for the 12-tablet group. These results suggest that this nutritional supplement may play a role in the management of women with PMS.