The mixtures of triose reductone (TR) and several thiol-containing compounds were heated at 90℃ for 4 hr and the browning intensity and variation of UV and visible absorption spectra of the reaction mixture measured. The reaction of TR with cysteine (Cys), penicillamine (PSH) or glutathione (GSH) at pH2 caused a marked browning, probably based on the reaction of TR with amino groups in their molecules. The browning intensity of the reaction mixture of TR and N-acetyl-L-cysteine (NAC) or sodium thioglycollate (STG) was higher than that of TR, suggesting that TR can react with SH groups. The 1:1 reaction system of TR and thiol-containing compounds caused higher browning than the 1: 2 reaction system. With the reaction advanced, the UV absorption characteristic of TR decreased in all reaction systems. The increase in the absorption at near 230 and 310 nm and at the wavelength range of 340 to 460 nm, implying the formation of intermediate product, was also observed. Furthermore, the spots which are positive for 2, 6-dichlorophenol indophenol and palIadium chloride were detected thin-layer-chromatographically in the reactions of TR with PSH, GSH, Cys and NAC. These results suggest that TR reacts with SH groups of thiol-containing compounds to produce the thiol reductions as intermediates.