Raman microspectroscopy was used to characterize normal and malignant hepatocytes in both cultured cells and human liver tissues. Consistent spectral changes were observed, including intensity increases at 1040 and 1083 cm(-1) with malignancy. A loss of intensity at 1241 cm(-1) was also observed in cancer cells, but was obscured in tissues by the overlap of a 1253 cm(-1) band, thought to originate from heme proteins. Normal liver tissue also differed from both the malignant tumor and its accompanying cirrhotic tissue at 1182 cm(-1). These results demonstrate the potential usefulness of Raman spectroscopy in clinical diagnosis, and investigations into the source of the observed spectral changes will provide information on the underlying mechanisms of carcinogenesis.