Pyruvate (glyoxylate) aminotransferase from rat liver peroxisomes was highly purified and characterized. The enzyme preparation has a mol.wt. of approx. 80,000 with two identical subunits, and isoelectric point of 8.0 and a pH optimum between 8.0 and 8.5. The enzyme catalysed transamination between a number of L-amino acids and pyruvate or glyoxylate. The effective amino acceptors were pyruvate, phenylpyruvate and glyoxylate with serine, and glyoxylate and phenylpyruvate with alanine as amino donor. These properties and kinetic parameters of the enzyme are remarkably similar to those previously described for mitochondrial alanine-glyoxylate aminotransferase isoenzyme 1 from glucagon-injected rat liver [Noguchi, Okuno, Takada, Minatogawa, Okai & Kido (1978, Biochem. J. 169, 113-122].