The preparation of reagents, suitable for radioimmunoassay of 17-hydroxy-4-androsten-3-one /epitestosterone/ in body fluids is described. It includes a simplified synthesis of the immunogen, epitestosterone-3-/O-carboxymethyl/oxime coupled to bovine serumalbumin, its characterization and preparation of the radioligand [125I] iodohistaminyl derivative of epitestosterone. The assay protocol for epitestosterone detection in urine avoiding extraction is described and the reliability criteria of the method are given.