19-nortestosterone (nandrolone) is an effective anabolic steroid and its abuse for increasing sport performance is forbidden and prosecuted as doping. For antidoping control determination of nandrolone metabolites, 19-norandrosterone and 19-noretiocholanolone is used. However, 19-nortestosterone was identified as a steroid of endogenous origin in men and as its urinary excretion is under various external influences, selection of a correct limit value of the allowed concentration of nandrolone metabolites is disputable. In addition, nandrolone may find its way to the athlete even as a part of normal nutrition, e.g. steer or boar meat or bowels or as a part of nutritional supplements popular in athletes.

        Key words: 19-nortestosterone, nandrolone, 19-norandrosterone, 19-noretiocholanolone, normal excretion, exogenous origin.