Present structure of small flat-bottom valleys («Balkas») reflect s o r e features of their evolution. Majority of balkas at the Central Chernozemic and adjacent regions keep some traces of periglacial relief-forming processes which acted during several cold phases of the Pleistocene. Balkas of Holocene age are conspicuously different in morphology. As balkas contained no permanent flow, their evolution during the Pleistocene and the Holocene was somewhat different from that of river valleys.