Nandrolone is an anabolic steroid on the WADA List of Prohibited Substances. Mass spectrometry testing for nandrolone is accurate and reliable, and has been part of the routine anti-doping menu for many years. The science of anti-doping continues to evolve daily, and WADA regularly assists in making certain that the testing practices and techniques of accredited laboratories remain in step with scientific advances. This is done by providing information and operating instructions to accredited laboratories as science evolves. Recent scientific research suggests that, in very rare cases, and under certain special conditions, a chemical reaction may occur in a vial containing urine. This phenomenon is described as “unstable urine.” This phenomenon is brand new. In the last months, a few WADA-accredited laboratories noticed never-before-seen abnormal steroid profiles in rare urine samples containing nandrolone. They investigated further and alerted WADA about this new phenomenon. Subsequently, WADA has instructed all accredited labs to perform “stability tests” on urine samples with nandrolone concentration from 2 to 10 Ng/ml that show abnormal steroid profiles (see criteria in the attached scientific memo). Should the “stability test” reveal “unstable urine”, the laboratories won’t have to report an adverse analytical finding. At the same time, WADA is supporting a research project to better understand the chemical process creating this new “unstable urine” phenomenon. The 2 Ng/ml threshold for adverse findings of nandrolone remains unchanged. A copy of the May 2005 non-confidential scientific memo to WADA-accredited laboratories is attached.