Adult female dogs or pony mares were subjected to a nonlethal dose of CCl4 (0.5 ml/kg body wt). Amounts of several plasma enzymes thought to be indicative of hepatic disease were monitored. Plasma enzymes alanine aminotransferase, aspartate aminotransferase (AST), alkaline phosphatase (ALP), arginase, gamma-glutamyltransferase (GGT) and iditol dehydrogenase (ID) and total plasma bilirubin were determined in these animals before and after the administration of CCl4. In the dog, GGT was not significantly increased but ALP values increased during days 1-6. In the pony, GGT was significantly increased during the entire course of the study but ALP exhibited only small, transient (though significant) increases. Responses of ID, AST and ALP were unremarkable when compared between the pony and dog. Total bilirubin significantly (P .ltoreq. 0.05) increased from days 1-4 (pony) or days 5-8 (dog) after CCl4 dose but returned to or decreased below base-line values. Animals did not have evidence of icterus at any time. The dog and pony were distinct clinical entities and only the appropriate laboratory tests for each species should be used to provide information for the clinicopathologic evaluation of hepatic disease