The mutagenic activity of the vine stabilizer, sodium salt of 3-(5-nitro-2-furyl)acryl acid (5-NFA), was studied. Use was made of a cytogenetic analysis of mouse bone marrow cells, the dominant lethality test on male mice, analysis of chromosome aberrations in human lymphocyte culture and the Salmonella typhimurium test with metabolic drug activation in the body of mice. 5-NFA was administered intragastrically or given in drinking water. In tests on somatic and sexual cells of mammals, 5-NFA did not manifest mutagenic activity. The preparation increased the frequency of mutations in Salmonella on administration to mice in doses amounting to 1/5-1/4 of or exceeding the LD50.