AbstractA gas‐chromatographic (g.l.c.) method with electron‐capture (e.c.) detection is described for the simultaneous quantitative determination of nanogram concentrations of 2‐ethylamino‐3‐phenyl‐norbornane (Fencamfamine, REACTIVAN®) and its metabolite 2‐amino‐3‐phenylnorbornane in urine.The renal excretion of fencamfamine and its metabolite after oral administration to humans was followed over a period of several days. The excretion of both substances was affected by urinary pH. Excretion peaks were obtained 2–4 h after ingestion and the total amount excreted during 80 h varied from 11.9 to 33.2 per cent. Based on urinary values, the biological half life of fencamfamine was 16 h.The intake of acetazolamide shortly after fencamfamine resulted in a decrease of the fencamfamine excretion and a suppression of the metabolite output during at least 10 h. Acetazolamide did not influence the percentage of the doses excreted during 80 h.No changes occurred in urinary fencamfamine or metabolite concentrations during storage of the urine