SummarySerum concentrations of arginase, gluta‐mic pyruvic transaminase (SGPT) and gluta‐mic oxaloacetic transaminase (SGOT) in dogs, cats, horses, cattle, sheep and pigs were determined before and after oral administration of CCi4at doses known to cause hepatic necrosis. Following CCI4administration, serum concentration of arginase and SGOT increased to a level of diagnostic significance in all animals. SGPT increased markedly in dogs and cats and marginally in 1 of 3 cattle and 2 of 3 pigs. In the surviving animals, the serum concentration of arginase returned to normal range much earlier than SGPT or SGOT.Based on the CCI4experimental toxicity results of this study, an elevated level of serum arginase would appear to be a reliable indicator of hepatic necrosis in both small and large animals whereas SGPT would be a reliable indicator of hepatic necrosis only in dogs and c