Percutaneous absorption was studied in patients following topical application of betametahsone 17-benzoate cream and gel with occlusion by means of a sensitive and specific radioimmunoassay method. Concentrations of betamethasone 17-benzoate in plasma were between 0.3 and 5 ng/ml, indicating approximately 0.05 to 0.3% of the steroid applied to the skin was detected in plasma. Plasma betamethasone 17-benzoate levels increased in proportion to the amount of the steroid applied to the skin. High correlation between plasma betamethasone 17-benzoate levels and percent inhibition of plasma cortisol was also observed. Approximately 3 ng/ml levels of betamethasone 17-benzoate in plasma induced 90% inhibition of plasma cortisol. The data suggest that betamethasone 17-benzoate in gel base was more readily absorbed than in cream base.