A new method for mutagenicity testing of carcinogens is proposed in this paper. Mutagenic activity is examined through monitoring of the growth situation ofSalmonella typhimuriumTA98 strain with a series piezoelectric quartz crystal (SPQC) sensor. This method needs no immobilization and preincubation of microorganism, and is simple and rapid. It can be applied to detect mutagen directly. When it was used to study the mutagenicity of dimethyl sulfate, the test time was 4 h at 37°C. There was a good linear relationship between frequency shift and the dose of mutagen in the range 2.5-20 μg/mL and the regression equation was ∠F = 53.82 + 3.81C. Some experimental conditions are also discussed in detail.