In order to collect a large number of Drosophila act88F mutants for valuable information regarding the normal actin function, we have devised an efficient genetic scheme and a rapid screening method to obtain dominant flightless mutants of third chromosome. After mutagenesis with ethylmethanesulphonate(EMS), we screened approximately 120,000 individuals for Drosophila dominant flightless mutants of third chromosome by using these method and twenty-three mutations were isolated. Recombination mappings of mutated gene locus in these and additional twenty dominant flightless mutants of third chromosome isolated previously by K. Mogami and Y. Hotta(Mol.Gen.Genet.183:409-417,1981) revealed that twenty-five mutations among them were located near or at the act88F locus.