Serum prolactin of 238 normal adults were determined by radioimmunoa-ssay using ~(125)-hPRL labelled in this laboratory and a non-equillibrium incu-bation prccedure. No significant difference exists between different sex or age groups. The overall mean was 18.9ng/ml and the range of m±2SD was 0.5-37. 3ng/ml. Determination of 292 cases of various pathological states showed that serumprolactin remained within normal range in Klinefelter's syndrome, Sheehan'ssyndrome, dwarfism, IDDM, NIDDM, secondary amenorrhe...