Patients with fatty liver diagnosed by computed tomography (CT) were studied clinically. Diagnostic criteria of fatty liver by CT was that the ratio of CT value of the liver to that of the spleen was less than 0.90. In cases of fatty liver, hepatic volume was significantly more increased (p<0.01) than normal controls, but volume of the spleen was not more increased. Fatty liver was diagnosed by CT in thirty eight cases. These cases were divided into four groups according to causes of fatty liver.The first was obesity group (fifteen cases), the second was alcohol group (fourteen cases), the third was DM group (four cases) and the fourth was group of unknown origin (five cases). Values of GOT/GPT (OP ratio), γ-GTP, CHE, LAP and ALB were significantly different (p<0.01) between obesity and alcohol group. Many cases of obesity group showed hypercholinesterasemia, but in many cases of alcohol group values of cholinesterase were lower than normal range.