Different biological systems have been used to test growth inhibition and genetic effects produced by irradiated sucrose. Sucrose has been irradiated with rays froma source of Co-60 with 2 Mrads. The irradiated sucrose produces a strong inhibition on the growth of cell of the wild carrot Daucus carota. The growth of two strains of E. coli K 12 was also inhibited by irradiated sucrose which also dramatically affects survival of the cells. Only a slight effect was noted on a third strain of E. coli, while a strain of B. subtilis was totally resistent to irradiated sucrose. In Aspergillus nidulans irradiated sucrose does not affect either viability or mutation and somatic segregation frequencies.