A double blind, crossover study of fibrinolytic enhancement treatment using stanozolol has been performed in primary Raynaud's phenomenon and in systemic sclerosis. The outcome criteria included subjective evaluation, clinical examination, physiological measurements of peripheral blood flow, and fibrinolytic measurements. Nineteen patients entered and 11 completed the study of primary Raynaud's phenomenon. There was nonsignificant evidence of improvement in peripheral blood flow. Twenty four patients entered and 17 completed the study of systemic sclerosis. There was marked objective but not subjective evidence of improvement in the peripheral microcirculation during the stanozolol treatment period. There was also a nonsignificant improvement in dermal sclerosis. There were improvements in fibrinolytic activity during the stanozolol treatment period. There was no alteration in fibrinolytic reserve as measured by 1-desamino-8-D-arginine vasopressin stimulation, however. Although adverse events were common in both treatment periods, withdrawals predominantly occurred during the period of treatment with stanozolol and were principally due to anabolic problems. There does not seem to be any indication for the use of stanozolol in primary Raynaud's phenomenon. Fibrinolytic enhancement with stanozolol does appear useful in treating the microvascular features of systemic sclerosis.