[1,1-T]-ethanol,:1,1-T]-propanol and [1,1-T]-butanol exhibit small isotope effects (kH/kT=1.3-1.8) in the liver alcohol dehydrogenase catalyzed reaction NAD® + alcohol ⇌aldehyde +NADH+H®. Presence of semicarbazide (with [1,1-T] -ethanol) or substrat inhibition (with [1,1-T] -butanol, 2.10-2-m.) raises the isotope effect (up to 4.1 at 25 °C) by introducing partial irreversibility to the interconversion step of the ternary complexes. This is in agreement with the Theorell-Chance mechanism as extended by DALZIEL. Thus, isotope effect determinations confirm both, the presence of ternary complexes and their kinetic insignificance for lower aliphatic substrates. The results are markedly different from analogous kinetics with the yeast enzyme.