3β-Hydroxyandrost-5-en-17-one (I) was reduced catalytically with carrier-free tritium. The product was mainly 3β-hydroxy-5α-androstan-17-one (II), which was converted to androst-4-ene-3, 17-dione (VI) with a loss of 43% of the label. 6β-Bromination and 6β-methoxylation was carried out on VI with little loss of label, indicating that the tritium at C-6 was alpha orientated. Chemical and kinetic experiments established that the additional label was at C-7α. The distribution of tritium in the reduced product II was 43% 5α, 35% 6α and 22% 7α.