The present study was carried out to know maintaining allozyme polymorphism by fitness components and mating behavior among $alpha$-GPDH and Est-$eta$ genotypes in Drosophila melanogaster. In fitness components, fecundity and eclosion rate were showed heterosis and those of FS ($alpha$-GPDH)ㆍFS(Est-$eta$) were the most dominant among genotypes. In mating behavior, each genotype was showed significant sexual isolation and all individuals favored to F of $alpha$-GPDH and S genotype of Est-$eta$, especially S genotype of Est-$eta$. Therefore, the maintaining allozyme polymorphism nay be concerned with the heterosis in fitness components and mating behavior among genotypes.