Oxidative stress may represent a common link between chronic liver damage and hepatic fibrosis. In the present study, we investigated activity changes of sphingomyelin catabolic enzymes, such as sphingomyelinases and ceramidases by using dimethylnitrosamine (DMN)-treated Sprague-Dawley (SD) male rats hepatic fibrosis model as a hepatic fibrosis model. Twenty rats divided into five groups received: (1) saline; (2) DMN for 1 week, (3) DMN for 2 weeks, (4) DMN for 3 weeks, and (5) DMN for 4 weeks by intraperitoneally 10 mg/kg of body weight for three consecutive days a week. Activities of acidic and neutral sphingomyelinases and acidic, neutral and alkaline ceramidases were measured in the liver and kidney from DMN-treated rats. We found increased ceramidase activities from 2-week and/or 3-week DMN treated rat livers compared to control rat liver. Acidic sphingomyelinase and alkaline ceramidase activities were significantly increased in 3-week DMN-treated rat kidneys compared to control rat kidney. Therefore, sphingolipid metabolizing enzymes and sphingolipid metabolites are supposed to be involved in liver fibrosis, although further investigation is necessary to elucidate meanings of sphingolipids during the liver fibrosis