There have been occasional reports of acute respiratory and skeletal muscle weakness in intensive care unit patients treated with massive doses of corticosteroids. However, in this setting the concomitant use of other drugs may have influenced the finding. In this study the effects of 5 days of treatment with high doses of steroids in consecutive patients with acute lung rejection after transplantation were systematically evaluated. Maximal inspiratory pressure during phrenic nerve stimulation and peak torque of isokinetic contraction of the quadriceps and hamstring muscles were measured objectively. Compared to the pretreatment condition, approximately 45% of patients showed acute generalised muscle weakness that recovered after approximately 2 months. This demonstrates muscle weakness induced by steroids within patients.