A new recessive mutant, hooked leg (h), was discovered from an inbred strain of Aedes togoi. Tarsi of hindlegs in the mutant are bent sharply like hooks and the hindlegs of some homozygotes for H are sometimes broken off by hooking onto the pupal skins upon emergence. Homozygotes exhibit complete penetrance almost uniform expression. The midlegs of the homozygotes are also slightly affected. Linkage studies indicated that the H allele is located between the M (sex allele) and S (straw-colored larva) loci on linkage group I and that the recombination distances are 16.5 map units for M-H, 39.0 for H-S, and 42.4 for M-S.