BACKGROUND Interleukin (IL)-12 is a proinflammatory cytokine produced by antigen-presenting cells upon stimulation by diverse stimuli. This study aimed to explore the relationship between IL-12 serum levels and different stages of alcoholic liver disease, alcoholic intake status and abstinence from alcohol. METHODS A total of 35 healthy controls without alcohol consumption and 94 patients with alcoholic liver disease (17 with alcoholic steatosis, 37 with alcoholic hepatitis, 40 with alcoholic cirrhosis) were included. Their serum IL-12 levels were measured and followed-up at the 3(rd), 6(th) and 9(th) months. Data were further analyzed according to abstinence from alcohol or not. RESULTS Mean serum IL-12 levels were higher in the alcoholic hepatitis group (163.1 +/- 57.8 pg/mL) than in the alcoholic liver cirrhosis group (110.5 +/- 41.6 pg/mL) and alcoholic steatosis group (74.4 +/- 26.2 pg/mL). All of these 3 alcoholic groups had higher serum IL-12 levels than the control group (39.3 +/- 8.3 pg/mL; p < 0.02). Among the patients who abstained from alcohol, there was no difference in serum IL-12 levels between control and steatosis patients at the 9(th) month, but the serum IL-12 levels of the hepatitis and cirrhosis groups were still higher than in the control group (p < 0.001 and p = 0.001, respectively). In addition, the patients who continued to drink alcohol had higher serum IL-12 levels than those who abstained from alcohol in the steatosis, hepatitis and cirrhosis groups. At the cut-off value of 54 pg/mL, IL-12 had good sensitivity and specificity in the diagnosis of alcoholic liver disease. CONCLUSIONS Serum IL-12 levels reflected the different stages of alcoholic liver disease and can represent the status of continuous alcohol consumption. It has the potential to be a biomarker of alcoholic liver disease.