This paper summarizes result of research on the cyanobacterial S-layers obtained between 1989 and 1995. In 12 chroococcal strains (of six species) and in one filamentous strain, S-layers were found by electron microscopy and characterized. Laser diffractometry permitted a more detailed analysis. Most S-layers were of a hexagonal lattice (p6 symmetry), their subunit center-to-center spacing raning from 10.7 nm (Microcystis cf. aeruginosa, natural population, Brno 1993) to 17.6 nm (Synechocystis aquatilis, strain MARKLE 1430/3). Tetragonal protomer lattice (p4) was found in Cyanothece cedrorum, strain LEFEVRE 1973/19 (8.3x5.4 nm spacing) and in Synechococcus bigranulatus, strain KOVROV 1972/8 (10.8x8.6 nm spacing). Strip-latticed (p2) S-layers were exposed on cells of Cyanothece aeruginosa, strain KOCH 1974 (8.6 nm) and of Leptolyngbya hypolimnetica (9.4 nm spacing), which is one of the first findigs of S-layers on filamentous, multicellular organism. The S-layer of Cyanothece cedrorum is the finest ever seen in cyanobacteria.