The amount of alpha-bromocinnamaldehyde (BCA), an anti-mildew agent, in some commercial products, was examined by high performance liquid chromatography (HPLC) using the following conditions: column, Nucleosil 50-5 (Nagel, 250 mm x 4.6 mm i.d.); mobile phase, hexane-chloroform (12:5); flow rate, 1.0 ml/min; detector, ultraviolet detector; detection wavelength, 290 nm. Large amounts of BCA were detected in anti-mildew mat (10,700-43,500 micrograms/g), anti-mildew cloth (1,100 micrograms/g) and BCA gel (10,050 micrograms/g). BCA was also tested for mutagenicity against Salmonella typhimurium TA100, TA98 and TA2637, with and without metabolic activation (S9 mix). The result showed that BCA was a very potent mutagen and induced 1.0 x 10(6) of revertants per mg against TA100 without S9 mix. The mutagenicity decreased to 1.3 x 10(4) revertants per mg in the presence of S9 mix.