The species and karyotypical composition of malaria mosquitoes in Moscow and in the Moscow Region have been examined. A cytogenetic analysis in the Moscow Region has revealed 3 types of malaria mosquitoes: Anopheles claviger Mg., An. maculipennis Mg., and An. messeae Fall. An. messeae predominates in the Solnechnogorsk and Noginsk Regions, An. maculipennis prevails in the Ramensk and Serpukhov Regions. In the combined habitats, the ratio of two predominant types has been ascertained to vary during a season. The proportion of An. maculipennis increases by the end of summer and decreases during hibernation. The more northern type of An. messeae has been shown to be superior to An. maculipennis in fertility. Thus, the increased relative size of An. maculipennis during summer is due to the higher viability of the larvae of this type. In the Moscow water reservoirs, the larvae of both types develop concurrently; the proportion of An. messeae is 89.8%. The high level of chromosomal variability was found in the urban populations of An. messeae by the inversions of XL1, XL3, 2R1, 3R1. A role of chromosomal variability in the adaptation of mosquitoes to urban conditions is discussed.