The properties of heterochromatin from polytene chromosomes of the malaria mosquito Anopheles messeae Fal. and A. atroparvus V. Tiel. were studied by various methods of differential staining and by hybridization in situ with two repetitive DNA sequences of Drosophila melanogaster. In malaria mosquito, the heterochromatin was heterogeneous. Two forms of alpha-heterochromatin were revealed: pericentromeric and intercalary heterochromatin, which is localized within the internal chromosome regions.