Phosphogluconate dehydrogenase (PGD) and xanthine dehydrogenase (XDH) were genetically studied by agar gel electrophoresis in the mosquito Aedes togoi. Adult homogenates displayed banding patterns with one zone of activity of either enzyme. Eight backcrosses were conducted to map the two loci, Pgd and Xdh, to linkage group III with the following arrangement: Pgd--(ca. 15 map units)--bl (bleached pupa)--(ca.5)--y (yellow larva)--(38.0 +/- 1.7)--pm (plum eye)--(6.1 +/- 0.9)--Xdh. All Pgd and Xdh loci thus far mapped in other mosquito species are reviewed for a comparison with those in this species.