: A mild prevalence of multiple sclerosis (MS) is present in females (2:1). To elucidate the pathogenetic role of sex steroids on the disease, we studied 76 women affected by MS, compared to 50 healthy women (mean age +/- SD, 34.9 +/- 0.9 vs. 33.4 +/- 1.7 years). The menarche was at mean age of 12.3 +/- 0.2 vs. 12.4 +/- 0.2. Interval between menses was 28.0 +/- 0.3 vs 27.8 +/- 0.3 days, with duration of menstrual flow of 5.0 +/- 0.2 vs. 5.0 +/- 0.2 days. Oligo- or amenorrhea was present in 20% of patients and in 16% of controls. Oral contraceptives were assumed by 21% of patients and 34% of controls (n.s.). Premenstrual symptoms were found in 43% of patients and in 46% of controls (n.s.). The incidence of hyperandrogenism (greasy skin, acne and hirsutism), evaluated by a specific questionnaire, was higher and statistically significant in MS patients than in controls (28% vs. 10%, p<0.05). Further studies, including a complete clinical and laboratory evaluation of gonadal function, are necessary in order to clarify whether hyperandrogenism may influence MS disease activity.