Results of randomised trials and open studies in 291 patients with severe persistent breast pain in whom breast cancer had been excluded showed that drug therapy produced a good or useful result in 77% of those with cyclical mastalgia and 44% of those with non-cyclical mastalgia. In patients with cyclical mastalgia good or useful responses were obtained with danazol in 70%, with bromocriptine in 47%, and with evening-primrose oil in 45%. The equivalent response rates in patients with non-cyclical mastalgia were 31%, 20%, and 27% respectively. Progestagens were not effective in either group. Failure to respond to one drug did not preclude response to a different drug. Patients with Tietze's syndrome did not respond to drug therapy, but 7 out of 10 responded to injection of lignocaine and hydrocortisone around the affected costochondral junction.