The chromocenter organization and the relationship with the nuclear envelope were studied in Anopheles messeae Fall. malaria mosquito. The interchromosomal contacts within the chromocenter were shown to be formed by both alpha- and beta-heterochromatin. In the pericentric regions of all chromosomes and in highly repeated sequences localized mostly in alpha-heterochromatin, the incorporation of the moderate He-T repeat of D. melanogaster was also found. Each chromosome was shown to have an independent contact to the nuclear envelope via certain beta-heterochromatin loci. The morphology of the Y chromosome, which is also capable of forming ectopic contacts within the chromocenter boundaries, was studied.