The effects of ibuprofen (400 mg), naproxen sodium (250 mg) and paracetamol (500 mg) on intrauterine pressure and menstrual pain was assessed in 12 women with dysmenorrhoea in a double-blind parallel study. Intrauterine pressure was recorded with a microtransducer catheter for 4 h and resting pressure, active pressure, frequency of pressure cycles and the area under the curve were analysed in 30-min periods. Ibuprofen, in a single oral dose of 400 mg, significantly reduced resting pressure, active pressure, the frequency of pressure cycles and the area under the curve and this was associated with a significant reduction in pain intensity. Neither paracetamol nor naproxen sodium effected significant changes in intrauterine pressure or pain score.