The plasma HGH concentrations were assayed in total 138 cases by the radioimmunoassay. The groups of control, typhoid fever, epidemic hemorrhagic fever, tuberculous meningitis and other febrile diseases were studied, also were the groups of hyperthyroidism, acromegaly and hypopitutarism. Insulin stimulation test was performed in control, typhoid fever and hypopituitarism. In the control group, the plasma HGH concentration in fasting (early morning) was $2.06{pm}1.183m{mu}g/ml$ and its upper limit was $4.5m{mu}g/ml$. No sexual difference was observed. By the insulin stimulation, plasma HGH concentration had rised to the peak level of $24.1{pm}15.71m{mu}g/ml$, 60 min. after the intravenous insulin injection, then decreased to the normal level progressively. In typhoid fever, fasting HGH concentrations in febrile state and in defeverence were $2.5{pm}1.35m{mu}g/ml;and;2.2{pm}3.32m{mu}g/ml$ respectively, showing no significant difference with the control group. However, the levels of individual cases ranged widely, conpared with the control group. The response to the insulin stimulation test was similar to the control group. In epidemic hemorrhagic fever the HGH concentrations in oliguric phase, in diuretic phase and in convalescence were $4.2{pm}3.71m{mu}g/ml,;2.2{pm}1.30m{mu}g/ml;and;3.4{pm}3.01m{mu}g/ml$ respectively. No significant differences were observe compared to the control, but they showed wide range of plasma HGH levels. In tuberculous meningitis, the fasting HGH concentration was $2.9{pm}1.42m{mu}g/ml$. In the other febrile diseases, the value was $2.5{pm}2.23m{mu}g/ml$. In 4 cases of hypopituitarism, the fasting HGH concentration was $2.3{pm}0.42m{mu}g/ml$ and ranged normally. However, the response to the insulin stimulation test was not observed. Very high plasma HGH concentrations were observed in acromegalic patients.