Physiological toxic and mutagenic effects of gramoxone in Drosophila melanogaster were invetigated. Gramoxone was highly toxic on the development, resulting in of lowering the viability and in prolongation of the developmental times. Adults treated with gramoxone during the developmental stages caused a lowering of the productivity and a little chinge in protein quantity. But the effect on the sex-linked lethal mutagenesis was found to be negative. The order of mortality causing ado리t stoa형e feeding to gramoxone in the D. melanogaster complex was like this ; D. mauritiana, D. sechellia, D. simulans and D. melanogasteu Two species of the D. yakuba complex were alike. Those results were more or less correlation with speciation of the D. melanogaster subgroup. KEY WORDS : gramoxone, toxic and mutagenic effects, Drosophila meianogaster sub-group