We have examined serum alpha-fetoprotein (AFP) concentrations in the pre- and post-orthotopic liver transplantation (OLT) period of a population of 19 adult patients. (Five with secondary hepatic malignancy and fourteen with primary hepatic cancer). In pre-OLT, rises in serum AFP levels are indicatives for hepatocellular carcinoma (HCC): six of our nine cases of HCC were associated with the increase in serum AFP concentration, but none of the non-hepatocellular primary cancers and only one of the five secondary malignancy (hepatic metastasis of breast carcinoma with serum AFP values around 20 ng/ml). In pre-OLT, AFP values correlated with viable tumor mass rather than tumor:volume. In post-OLT, rises in AFP concentrations may be explained either by recurrent hepatic cancer or by hepatic post-necrotic regeneration. In this case, the increase in serum transaminasis is an important help for differential diagnosis.