The authors report 24 cases of diffuse nodular regenerative hyperplasia of the liver (DNRH) seen in a General Hospital during the last 9 years (prevalence: 3'1/100,000, incidence: 0'34/100,000). DNRH was diagnosed in 0.52% of the liver biopsies and 0.72 of the autopsies. These results suggest that DNHR is probably more frequent than suspected, and 1 DNRH was seen for each 39 biopsied cases of liver cirrhosis. Fourteen patients did not have hepatic symptoms. Portal hypertension was present in 9 cases. The biochemical disturbance most frequently found was a moderate elevation of GGT and APh, associated with slight elevation of SGOT, SGPT and bilirubin levels. Normal liver function tests could be seen (3 cases). Previous exposure to potentially hepatotoxic drugs or chemicals was discovered in 15 cases (62.5%). Diseases associated were circulatory disturbances (6 cases), autoimmune disease (5 cases), hemopathies (5 cases), and visceral carcinomas (4 cases). Two patients were recipients of renal transplant. Nodules distributed through the whole liver tissue were found in 16 cases, while 8 patients showed areas of normal parenchyma in their livers. Impairment of small hepatic vessels was detected in 16 cases. Some uneven cytologic findings were discovered: clusters of small basophilic cells (4 cases), large clear cells (8 cases), and dysplastic hepatocytes (10 cases), which suggests that DNRH could be a preneoplastic condition.