It is well known that ornithine-ketoacid transaminase(OKT) catalyzes the interconversion of ornithine and gluaamic-δ-semialdehyde with concomitant interconversion of α-ketoglutarate and glutamate in animal tissues. In 1963 Peraino and Pitot reported some properties of OKT using partially purified enzyme. In 1964 we reported the purification of the enzyme to a single component by ultracentrifugal and electrophoretic analysis. Strecher also reported some important kinetical properties using partially purified enzyme. Recently, we purified and crystallized the enzyme in good yiels from rat liver. This is reported in this paper with some physicochemical properties of OKT. © 1968.