A primary toxicological evaluation of diazoline was carried out, with a calculation of the Ap-proximately Safe Level of Impact (ASLI) within air of populated areas. It was found that diazoline by the parameters of acute toxicity fours grade 4 (little hazardous substances according to the GOST 12.1.007-76). Diazoline expressed low irritating effect, when it comes into contact with the conjuncti-va, showing a significant cumulative activity. ASLI of diazoline in the air of populated areas is 0.1 mg/m3.