In this paper, a sex-dependent matrix game haploid model is investigated. F
or this model, since the phenotypes of female and male individuals are dete
rmined by alleles located at a single locus and are sex dependent, any give
n genotype corresponds to a strategy pair. Thus, a strategy pair is an ESS
if and only if the allele corresponding to this strategy pair cannot be inv
aded by any mutant allele. We show that an ESS equilibrium must be locally
asymptotically stable if it exists. (C) 2000 Academic Press.