The presence of the anabolic steroid boldenone in animals has become a research topic as its occurrence is proposed to be a marker for illegal hormone administration. However, boldenone can also be formed from β–sitosterol, a phytosterol present in animal feed, as well as from endogenous sources. The observations in animals together with the increased consumption of phytosterol-enriched foods in the western population lead us to the hypothesis that consumption of phytosterol-enriched foods may possibly lead to increased boldenone levels in humans. We performed a pilot study among female volunteers (n=10) to investigate whether boldenone concentrations in urine were detectable after consumption of 25 g/day of phytosterol-enriched margarines for one week. Urine samples were collected at day 0, day 3 or 4 and day 7. Urine of a sitosterolemia (a rare autosomal recessively inherited lipid metabolic disorder) patient was collected as a positive control case. No traces of boldenone were detected in either the volunteers or in the patient. In conclusion, there is no evidence of formation of boldenone in women after consumption of the recommended amount of phytosterol-enriched margarines.