Serum insulin and growth hormone responses to intravenous infusion of arginine were measured in 10 normal control persons and 13 age- and weight-matched nondiabetic psoriatics. The average peak insulin levels, 58.2 μU/ml for normal controls and 47.8 μU/ml for the psoriatics, were recorded at 30 min. The average growth hormone peak values, 20.1 ng/ml for normal controls and 17.8 ng/ml for the psoriatics, were recorded in most cases in 60 min. No significant differences were obtained between the normal controls and psoriatics.