We have explored the relationship of serum alpha-fetoprotein and macroregenerative nodules (MRNs), possible precursor lesions of hepatocellular carcinoma (HCC), and sought to demonstrate alpha-fetoprotein (AFP) expression in these nodules. One hundred and sixty-eight sequential adult cirrhotic resected livers were examined and MRNs were identified by standard criteria. Pretransplant serum AFP was available for 158 of these patients (normal < 20 ng/ml). One hundred and seventy-two randomly selected lesions, including ordinary and atypical MRNs, some containing microfoci of HCC, and HCCs were stained for AFP by immunohistochemistry. In the series, 12 cases had grossly apparent HCCs, four associated with high serum alpha-fetoprotein (p < 0.006). Forty-four cases had MRNs, 32 without grossly apparent HCC. Five of these 32 cases were associated with high serum AFP (not significant). Immuno-staining for AFP was seen in three specimens of HCC and in a cirrhotic nodule from a patient without HCC, but not in MRNs. 1) Neither the presence of MRNs--whether ordinary, atypical, or containing micro-foci of HCC--nor that of gross HCC is ruled out by a normal serum AFP. 2) Elevated serum AFP is not associated with the presence of MRNs. 3) MRNs rarely stain for tissue AFP.