To study the association between bone disease and long-term steroid administration in asthmatics, we reviewed the hospital records of 128 patients over 40 years of age who had taken daily or alternate-day adrenal corticosteroids for at least a year and compared them with the records of 54 other asthmatics of similar age who had not required long-term administration of steroids. We found evidence in the records of a total of 58 fractures of the ribs or vertebrae in 14 of the patients who had received long-term steroid treatment (11 per cent) and no evidence of fractures in the patients who had not received long-term treatment. We also prospectively studied 30 hospitalized asthmatic patients between 20 and 70 years of age who had been screened for medications (other than steroids) or complicating diseases known to affect bone mineralization. Eight of 19 asthmatic patients receiving long-term steroid therapy had rib or vertebral fractures, whereas none of 11 matched patients not receiving such therapy had fractures. Furthermore, bone-density measurements of the distal and proximal radius by photon absorptiometry revealed that the trabecular, but not the cortical, bone mass was below normal in the former group of patients but not in the latter. Within the long-term steroid group, there was no significant correlation between bone density and dose or duration of steroid treatment. We conclude that long-term steroid therapy in asthmatic patients is associated with decreased trabecular bone density and an increased prevalence of rib and vertebral fractures.