Abstract. The article presents the materials of experimental research on the new defoliant of cotton "Phosphodef". By parameters of acute toxicity the studied preparation belongs to low hazardous compounds, IV class of hazard. The irritating effect of the preparations on mucous membranes of eyes and skin; cumulative properties of the preparation have been studied in acute experiments. Hygienic standards of the preparation in air, water, soil and food products; sanitary protection zones, terms of employment are scientifically proved. According to the research results, the use of defoliant "Phosphodeph" in agriculture from hygienic positions is not objectionable.