Four wallaroos (Macropus robustus) from a central California zoo colony of 22 died within a three week period. Histopathologic findings in all four cases were suggestive of toxoplasmosis. Brain, lung and heart were the most frequently involved organs. Within 4 months of the last death sera from nine colony members were tested for antibodies against Toxoplasma gondii using the indirect hemagglutination test. All nine had serological titers ranging from 1:64 to 1:131,072.