Abstract Objective: To compare efficacy and tolerability of drotaverine 80mg and ibuprofen 400mg in patients with primary dysmenorrhoea. Materials and methods: Nine-month, multicenter (11 study centers in Poland), randomised, double-blind, phase III study, conducted in two parallel group, included 345 women between the ages of 18 and 35, suffering from primary dysmenorrhoea with presence of moderate to severe pain in each of the last 3 cycles. Patients had regular menstrual cycles and used an adequate barrier contraception method with a negative pregnancy test before randomization. Patients were given 80mg drotaverine or 400mg ibuprofen and asked to assess the pain intensity rated on a 4 point categorical scale (0 - none, 1 - mild, 2 - moderate, 3 - severe) at baseline and 0.5, 1, 2, 3, 4, 5 and 6 hours after the first intake and evaluate the efficacy (excellent, good, fair, poor) at the end of the treatment period. They were also asked to asses the tolerance of the medication (excellent, good, fair, poor). Results: The weighted sum of pain intensity differences over the 6-hour observation period (SPID-6) was calculated. The pain intensity before the first intake was comparable in the two groups. At the time-points, the decrease of pain was always greater in the ibuprofen 400mg group, than in the drotaverine 80mg group and was maximum at the 4th hour in the drotaverine 80mg group (-1.2+/-1.18) and at the 3rd hour in the ibuprofen 400mg group (-1.7+/-0.99). 41,8% patients treated with drotaverine and 68,6% patients treated with ibuprofen assessed drug efficacy as excellent or good. Although the patients' global assessment of tolerability was significantly better (p=0.02) with ibuprofen 400mg (excellent or good: 86.8%), than with drotaverine 80mg (excellent or good: 78.4%), no relevant difference between the both groups was observed for frequency, nature, intensity and causality of the reported adverse events. Conclusions: After analizing the data statistically and clinically, significant differences in favour of ibuprofen 400mg were evidenced for efficacy criteria. Ibuprofen was more efficient and the effect was faster, than drotaverine in relieving pain in dysmenorrhoea. Both drugs were well tolerated. The reported adverse events were typical drug reactions or expected events in patients suffering from dysmenorrhoea.