The diversity of freshwater and inland saline planktic cyanoprokaryote microflora (cyanobacteria, cyanophytes) in Mexico depends on the wide variation of the biotopes in this country. There are no detailed studies, describing the planktic cyanoprokaryotic species from this region. This paper lists 51 planktic morphospecies, which were found in various water bodies in central Mexico during May 1992 and March-September 1993. Four new species (Cyanobacterium lineatum, Cyanotetras aerotopa, Anabaena fallax, Cylindrospermopsis taverae) are described, and important species commented. Various species characteristic for various types of reservoirs (volcanic lakes, lakes and artificial reservoirs with diverse trophic levels, hypertrophic pools, saline coastal lakes) were found. Taxonomic and ecological elaborations of the planktic cyanobacteria of Mexico (from an ecological, geographical as well as sanitary point of view – eutrofication, biomass production, toxicity) are urgently needed.