Introduction. In experimental toxicology, the selection of criteria characterizing the toxicological process play an important role in evaluating the effectiveness of the means of prevention and treatment of intoxication. Aim of the study: study of the dynamics, informativity and prognostic significance of rectal temperature at sulfur mustard intoxication in rats. Results of the study. The results showed that intramuscular injection of sulfuric mustard in rats in the range of doses from minimally lethal to absolutely lethal is accompanied by a dose-dependent decrease in rectal temperature at 3-days of intoxication. In the studied sample, the dividing capacity (AUC) of the rectal temperature index at the intoxication peak (3-d day) for mortality was 0,94 (95 % CI 0,8–0,91), which corresponds to excellent predictive ability. The sensitivity and specificity parameters for rectal temperature were 0,86 (95 % CI 0,8–0,91) and 0,90 (95 % CI 0,83–0,95), respectively. Conclusions. Rectal temperature values reflect the dynamics and severity of sulfur mustard intoxication in rats. This criterion has a high informative and predictive value in relation to the death and can be reasonably included in the program of evaluation of the effectiveness of the developed means of prevention and treatment of sulfur mustard.