The authors have summed up the results of development of enzymoimmunoassay (EIA) for the determination of testosterone (T) in human and animal blood plasma. The method is based upon the use of rabbit antiserum to testosterone-3-(0-carboxymethyl) oxim with bovine serum albumin as a binding system, a conjugate of T with horse-radish peroxidase as a marker, and the formation of the antigen-antibody complex was registered with a spectrophotometer of Cf-4a, Cf-16 and Cf-26 types. The method is highly sensitive (6.25 pg/test), specific and is characterized by high indices of precision. Close correlation between EIA and RIA results for the determination of a T level in human and simian plasma under physiological conditions as well as in some pathological conditions, associated with disturbed production of androgens, indicates the correctness of this method.