Abstract: This article introduces the method for the determinatiom of testosterone in plasma by RIA. The antigen was prepared by compling testosterone with BSA. Antigen was used for preparing the rabbit antiserum. The separation of immunocomplex from the free form of testosterone was accomplished by 1%Charcoal. The sensitivity of this method is 0.07 pmol. The interassay and intraassay coefficients of variation were 4.7% and 16.4% respectively The average recovery rate of testosterone was 100.4%. The article reported the plasma testosterone concentration of 158 normal subjects measured by this method. The male plasma testosterone level of the group old than 60 is lower than the group under 60, The female plasma testosterone level during the climacteric and menopause is lower than child bearing period and there is not statistic different in the different period of menstruation circle.

Key words: radio-immunoassay, testosterone