Proposals are under development to regulate the sale of dietary supplements for use by athletes to avoid accidental doping positives as a result of ingestion of contaminated supplements. This requires a knowledge of the amounts of contaminant that is likely to cause problems. The aim of the present study was to examine the urinary excretion pattern of nandrolone metabolites following 1µg, 2.5µg and 5µg doses of 19-norandrostendione in both male and female subjects. The quantity of 19-norandrostenedione administered in this study is representative of the amount previously reported as an undeclared contaminant in some dietary supplements. Given the speculation surrounding positive doping cases being attributed to ingestion of sports supplements contaminated with pro-hormones, this presents an important consideration for both athletes and doping agencies, as well as supplement manufacturers.