The fossil record from three sphagnum peat bogs situated at altitudes of 1400–1550 m in the Central Sredna Gora Mts (Bulgaria), consisting of 115 Diatomaceea species, 15 varieties and 2 forms, represents four diatom zones covering the time span of the last 10 ky. The diatom flora in the peat bogs emerged 8 ky ago. The fluctuating development of diatom communities was controlled by unstable water level, affected by local humidity and other climatic changes.