Taking B[a]P (benzo[a]pyrene) and NNK [4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone] as the target compounds, setting the concentration of cigarette smoke condensate (CSC) at 0 (CK), 0.0050, 0.010, 0.015, 0.020 mg/mL, that of NNK at 0 (CK), 0.005, 0.01, 0.02, 0.04 mg/mL and that of B[a]P at 0 (CK) , 0.00025, 0.00050, 0.00075, 0.0010 mg/mL, the synergic mutagenicity of the three components was evaluated. The results showed that: 1) CSC, NNK and B[a]P all induced mutation of Salmonella typhimurium strain TA98 and TA100 with obvious dose response. 2) There existed obvious synergism between B[a]P and CSC; high doses of B[a]P and NNK and low doses of CSC and NNK produced a weak additive effect. 3) Under different conditions, the combined effects induced by the three components on TA98 showed weak additive effect. By and large, the unified mutagenicity of NNK and B[a]P in the matrix of cigarette smoke showed the complexity of dose-response, time-response and sequence of action.