OBJECTIVE The prognosis of nonalcoholic fatty liver disease is determined by liver biopsy; steatohepatitis can be progressive whereas fatty liver is benign. Insulin resistance and increased hepatic-free fatty acids are central to the pathophysiology of this disorder. Our objective was to assess whether serum-free fatty acids, lipoproteins, and insulin resistance are increased in steatohepatitis compared with fatty liver and healthy controls, and thus may be potential noninvasive markers for liver disease severity. METHODS Fifteen subjects with biopsy proven nonalcoholic steatohepatitis, 15 with histological fatty liver, and 15 healthy controls were enrolled. Fasting serum glucose and insulin levels, serum-free fatty acids, HDL, LDL, and cholesterol were collected from each subject. Insulin resistance was calculated using the homeostasis assessment model. RESULTS Insulin resistance, LDL, and cholesterol-to-HDL ratio values were significantly higher in steatohepatitis, whereas HDL was significantly lower compared with both fatty liver and controls. Free fatty acids were similar in all groups. CONCLUSIONS Along with insulin resistance, serum LDL, and cholesterol-to-HDL ratio values increase with worsening severity of liver histology, and serum HDL values decline. Free fatty acids, however, do not vary between groups.