Investigations of mutagenic and embryotoxic action of ethidine were conducted on animals. The possibility of the mutagenic action of ethidine (in doses of 2500 and 1000 mg/kg of the body mass) was verified on mongrel albino mice through investigation of chromosomal aberration in the bone marrow cells. The embryotoxicity was studied on mongrel albino rats with introduction of the compound (in doses of 100 and 500 mg/kg to pregnant female rats at the time of implantation or organogenesis. On the 20th day of development the mass, length, external and internal developmental anomalies were noted along with observations carried on over the progency in the post-natal period. Opening of the eyes and the appearance of the hair tegmentum were recorded and dynamic changes in the body mass observed for a period of 2 months. In tests 14 mice were used from which 1300 cells were obtained and examined at the stage of metaphase and 50 female rats from which 307 embryos and 183 rattlings were studied in the post-natal period. Investigations failed to reveal any mutagenic of embryotoxic action of ethidine, nor its influence on the progeny in the post-natal period.