A prospective study has been carried out on 127 patients to test the accuracy of sonography in the diagnosis of diffuse liver diseases compared with histology based on percutaneous liver biopsy. Using sonographic criteria - size, margin, surface, elasticity, echo structure and sonic conductivity of the liver, hepatic veins and portal vein - and measuring the size of the gallbladder and the spleen, the following sonographic diagnoses were made: normal liver, fatty liver, fatty liver fibrosis, alcoholic hepatitis, chronic active hepatitis, cirrhosis. Sonographic diagnosis predicted histological diagnosis in case of normal liver in 56%, fatty liver 70%, alcoholic hepatitis 92%, chronic active hepatitis 63%, cirrhosis 79%. The specificity of sonography was 95%, the overall sensitivity was 82%: e.g. fatty liver 84%, chronic active hepatitis 93% and cirrhosis 79%. We conclude that sonography is an ideal screening method for detecting diffuse liver diseases. In cases of fatty liver and of cirrhosis it can spare the patient further invasive investigation. Furthermore, this method is suitable for evaluating the course of diffuse diseases of the liver, especially of toxic-nutritive liver damage and also of chronic active hepatitis.