The tumour suppressor genes, p53 and pRb, are known to play important roles in neoplastic transformation.While molecular routes to the uncontrolled growth of hepatocytes, leading to primary liver cancer have generatedconsiderable interest, the roles of p53 and pRb mutations in hepatocellular carcinoma (HCC) and hepatoblastoma(HB) remain to be clarified. We examined the immunohistochemical expression of p53 and pRb gene products in26 HCC and 9 HB, sampled into tissue microarray blocks. 10 (38%) of 26 HCC showed > 10% tumour nuclearstaining for p53 protein, 3 of these also being HbsAg positive. Conversely, none of 9 HB expressed nuclear p53immunopositivity. Some 24 (92%) HCC and 8 (89%) HB showed loss of pRb nuclear expression. Two of the 26HCC and one of the 9 HB showed >10% tumour nuclear staining for pRb protein. Our results suggest that p53does not have an important role in the development of HB but may contribute in HCC. There is also loss of pRbexpression in the majority of HCC and HB, supporting loss of pRb gene function in the hepatocarcinogenesispathway. However, a comparison of the staining profiles of p53 and pRb proteins in HCC and HB did not reveala consistent pattern to differentiate between the two types of tumours immunohistochemically. Hence the useof p53 and pRB protein expression has no contribution in the situation where there is a diagnostic difficulty indeciding between HCC and HB.