Open non comparative study for the evaluation of the efficacy and tolerability of the new piroxicam formulation, the Fast Dissolving Dosage Form tablets for sublingual administration in the treatment of primary dysmenorrhea. The 54 patients enrolled in the study have been treated with piroxicam sublingual tablets: 40 mg single daily dose for the first two days and 20 mg for the following three days for a total of 5 days of therapy to be repeated for two consecutive menstrual cycles. The drug efficacy was evaluated on the basis of variation of intensity in pain and associated symptoms, as cephalgia, nausea, vomiting, etc. The ability to perform normal daily activity has also been evaluated. The intensity of spontaneous pain in the first and second cycles showed a statistically significant improvement (p = 0.0001) only 15 minutes after drug administration. This improvement increased in the first and in the following days. The relief from pain was stronger in the second cycle, in fact none of the patients had to assume a further analgesic drug, as happened during the first cycle of therapy. As regards the symptoms associated to pain, as cephalgia and low back pain, they significatively decreased starting from the first cycle of treatment. The improvement became more marked during the second cycle of therapy. Local and systemic tolerability was good. Only 5 patients experienced systemic side effects in the first cycle, and 12 in the second cycle. Three patients experienced local side effects in the first cycle, and 1 in the second cycle. These effects were well tolerated and did not cause the treatment discontinuation. Moreover, most of the side effects occurred, as nausea and diarrhoea, are symptoms commonly associated to dysmenorrhea. In conclusion, piroxicam fast dissolving dosage form for sublingual administration, in the treatment of primary dysmenorrhea, showed its analgesic efficacy 15 minutes after the drug administration. It has also a good local and systemic tolerability.