The aim of this study was to determine the clinical effect of Foeniculum vulgare on primary dysmenorrhoea. Sixty virgin girls with complaints of dysmenorrhoea were enrolled in this study, out of which 50 cases were completed the course of treatment and were divided in two groups (study and placebo) and were under treatment for two cycles. In study group a capsule of 30 mg fennel extract, four times a day for three days from start of their menstrual period and in placebo a capsule containing wheat flour in same dose was administered. Intensity of pain was reported by using a 10 - point linear analogue technique. In study group the mean age of menarche was 13.1 ± 0.1 and onset age of dysmenorrhoea was 14.5 ± 0.1 years. Both groups were relieved but there was significant difference between study and placebo group. Study group shown more effective results than placebo in pain relief (P`0.05). Based on the observations, it can be concluded that, fennel is an effective herbal drug for menstrual pain.