The genotoxic activity of exhausts from one-shaft gas-turbine GTE-5 engine (30 kW) and a standard D-54A diesel (40 kW) have been studied. Thus, the extracts of soot from GTE-5 and D-54A induced reversions in Salmonella typhimurium both with and without metabolic activation: furthermore, extracts of soot from GTE-5 demonstrated a higher mutagenic activity. The direct mutagenic effect of the exhausts depended neither on the presence of BP nor on the other polycyclic aromatic hydrocarbons (PAHs). Most probably, it was connected with the presence of nitro-PAHs. The need for studying the PAH content in vehicle engines' exhausts and for taking into account their effect in the control and standardization is established.