Six recessive lethal mutants of Anopheles albimanus are described. Homozygotes for three of the autosomal mutants, viz., bar eye, dot eye and hairy, die during the last larval or early pupal stages; complete linkage data are lacking for bar eye and hairy but dot eye is tightly linked to red eye on the right arm of chromosome 2. Larval and pupal mortality is high for homozygotes of the other two autosomal mutants, diseased larva and lunate. Survival to the adult stage of the lunate type is about 60% for both sexes, and for diseased larva the rates differed according to sex, 15% for males and 3% for females. A general lack of vitality of the surviving adults has prevented the establishment of homozygous stocks. From analyses of linkage data, diseased larva and lunate were assigned to chromosome 2, most probably on the left arm. The mutant, bubble head, is on the X chromosome, and therefore is expressed only in the hemizygous male, which usually dies during the early pupal stage.