This lecture will focus on the diagnostic approach to a dog with persistently elevated serum liver enzyme activities. The diagnostic tests commonly used to evaluate the canine liver will be reviewed. A staged approach to evaluating these patients will also be presented. After the lecture attendees should be able to: 1) Recognize that increased serum ALT activities are generally more clinically relevant than increased ALP activities 2) Appreciate that increased serum liver enzyme activities can occur secondary to non-hepatic disease 3) Understand the uses and limitations of laboratory testing for hepatic disease in dogs 4) Develop a logical diagnostic plan when working up a dog with increased serum liver enzyme activities