An 8-yr-old captive, female common wombat (Vombatus ursinus) from Victoria, Australia was euthanased after an illness of 36 days manifested by lethargy, inappetance and terminal coma with respiratory failure. Toxoplasmosis was diagnosed during life by the Toxoplasma direct agglutination test (DAT) which showed a positive initial titre of 1:1,024 at 22 days after onset of illness and a four fold rise in titre to 1:4,098 2 wk later, just prior to death. The Toxoplasma modified agglutination test (MAT) remained negative over this time period. The serological diagnosis was confirmed by histological diagnosis of granulomatous encephalitis, focal myocarditis, interstitial pneumonia and severe adrenal cortical necrosis and the presence of tachyzoites of Toxoplasma gondii in large numbers within the focal necrotic lesions in the brain, myocardium and adrenal cortices. The serological response in the wombat differed from that of the typical eutherian which exhibits a reaction in both the DAT and MAT within 2 wk of infection with T. gondii. An incidental finding was calcification in the media of the ascending aorta and proximal parts of the major arteries.