Diabetes mellitus and hepatic lipidosis (fatty liver disease) are commonly encountered medical problems in pet cats. Both are associated with obesity. Prevention of these diseases by maintenance of an appropriate body weight would be ideal; however, weight control is difficult in many cats, and overweight cats with diabetes or fatty liver disease need specific treatments for these potentially life-threatening disorders. Current treatment options for diabetes in cats are limited to insulin, which must be given by injection, and to glipizide, a drug that exhausts the insulin-secreting cells of the pancreas over time. The only treatment that has improved survival rates in feline hepatic lipidosis is aggressive nutritional support via a feeding tube. In humans, relatively new anti-diabetic drugs called thiazolidinediones (TZDs) have been shown to improve insulin sensitivity and reverse fatty changes in the liver, not only in diabetics, but also in people with non-alcoholic fatty liver disease. Non-alcoholic fatty liver disease in people is similar in several ways to hepatic lipidosis in cats. Because of this, human TZDs such as pioglitazone would presumably be beneficial for treatment of diabetes and fatty liver disease in cats. The purpose of this project is to begin investigation of this drug in cats, so that it can later be used for clinical trials in cats with diabetes mellitus and hepatic lipidosis.