In the present study, the principle of synchronous luminescence (SL) is described for use in biomedical diagnostics. The SL method involves scanning simultaneously both emission and excitation wavelengths while keeping a constant wavelength interval between them. This SF procedure simplifies the emission spectrum and provides for greater selectivity and is used to detect subtle differences in the fluorescence emission of the biochemical species of cells and tissues. The SL method can be used to analyze tissue in vivo or to investigate spectral differences in normal and neoplastic cells in vitro. SL scans of skin tissues illustrate the use of the method. For in vitro diagnostics, a difference between the flourescent spectra of the normal rat liver epithelial and hepatoma cell lines were detected using synchronous fluorescence. The potential use of SF as s screening tool for cancer diagnosis is discussed.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.