Rat liver SAH-hydrolase is strongly inhibited by four stereoisomeric 4-(adenin-9-yl)-2,3-dihydroxybutyric acids (eritadenines). D-Eritadenine, which is the most effective of the four, inactivates the catalytic activity of SAH-hydrolase at IC50 = 1.2 .10-8 mol l-1 in the hydrolytic reaction. The enzyme is irreversibly inhibited (τ/2 = 1.6 min). The inactivation activity decreases in the order D-erythro(2R, 3R) L-erythro(2S, 3S) threo(2S, 3R) threo(2R, 3S) configuration.