Sixty female out-patients suffering from moderate to severe primary dysmenorrhea, aged 14-40 years (mean 27 years), entered this randomized, double-blind, 3-period, within-patient study, evaluating the efficacy and tolerability of diclofenac dispersible 46.5 mg (equivalent to 50 mg of diclofenac sodium), ibuprofen 400 mg and placebo taken up to 4 times daily for a maximum of 3 days. Pain relief was evaluated on a verbal rating scale (0 = none, 1 = slight, 2 = moderate, 3 = considerable, 4 = complete) at 0.5, 1,2,3,4,5 and 6 hours after the first dose; the weighted sum of pain relief scores over the 6-hour observation period was also investigated (TOTPAR-6). Pain intensity was assessed on a verbal rating scale (0 = nil, 1 = mild, 2 = moderate, 3 = severe) at baseline and at the above mentioned time points; the weighted sum of pain intensity differences at each time point was also analyzed (SPID-6). A rescue medication was permitted 1 hour or more after the intake of the test drug: in such cases the last value of pain intensity/relief scores was carried forward and used for the analysis. A global evaluation of efficacy and of trial medication as compared to her usual medication was performed by the patient at the end of each treatment period. Finally, adverse experiences were recorded throughout the study period. Analysis of covariance and Koch's adaptation of the Wilcoxon-Mann-Whitney rank sum test were used, where appropriate, for statistical analysis. Mean TOTPAR-6 values for diclofenac dispersible, ibuprofen and placebo were 16.5, 17.8 and 14.7, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)