OBJECTIVES: To estimate the direct treatment cost for patients with chronic hepatitis B (HBV) infection and the associated complications, including cirrhosis (compensated & decompensated), hepatocellular carcinoma (HCC) and liver transplantation (LT). METHODS: Relevant diagnostic data were collected from medical and financial records of HBV infected patients at the National University Hospital, the major hospital in Western Singapore. Each patient was followed up to five years. Clinical data collected included clinical diagnosis, laboratory investigations, ultrasound, and CT and liver biopsy results. Medical resource utilisation considered included the cost of consultation, outpatient care, medication, inpatient stays, and surgery and laboratory tests. The treatment costs due to chronic HBV infection and its related complications were specifically differentiated from those due to other medical conditions. Costs were annualized according to the years of follow up. In the estimation of every resource used, the cost was calculated by multiplying annual frequency and cost per item. The total annual direct cost for each patient (at 2003 value) was obtained by summing up all the defined items. RESULTS: During the data collection period (October 2002 until early April 2003), the case notes of 157 patients (116 chronic HBV, 13 compensated cirrhosis, 5 decompensated cirrhosis, 3 HCC, and 20 LT) were evaluated. The estimated average annual treatment cost of the different categories of patients was: chronic HBV: Sing$718.15 (range: $80.11-$4,690.05); compensated cirrhosis: Sing$1,194.79 (range $316.60-$2,203.60); decompensated cirrhosis: Sing$13162.55 (range: $7065.40-$25,638.80); and HCC: Sing$6628.97 (range: $4580.41-$8819.91) For LT cases, the estimated average cost during the hospitalization of the LT procedure only was Sing$73,673.10 (range: $47,435.48-$186,708.56) CONCLUSION: The results show that chronic HBV infection and its associated complications impose a significant financial burden to the health care system in Singapore. These data would provide valuable information for healthcare planners and providers in the management of HBV infection especially in the area of allocating resources.