Eight species belonging to the D. melanogaster subgroup were examined genetically and biochemically to analyze interspecific relationships. Hybridization tests and mitochondrial DNA analysis among the species have revealed that the most closely related pairs of species are the D. simulans-D. mauritiana within the complexes and the D. mauritiana-D. teissieri between the complexes. The four species belonging to the D. melanogaster complex were closely related to each other, however, the four species of the D. yakuba complex were observed to be somewhat more distantly related to each other than the rest. The genetic distances between species were obtained by the two-dimensional electrophoresis. The four species of D. melanogaster complex were closely related and the D. mauritiana-D. simulans pair was the closest (D=0.085). Among the D. yakuba complex, D. teissieri-D. yakuba pair was relatively closer to the D. melanogaster complex. D. erecta and D. orena were observed to be far more distantly related to each other than the others.