The sediment sequence from Budzewo (Skaliska Basin, north-eastern Poland) contains cladoceran records beginning from the early Holocene. A total of 33 Cladocera taxa were identifi ed in the entire sequence. The cladoceran fauna of the initial stage of palaeolake history in the Preboreal shows high similarity to early Holocene Estonian and Scandinavian records. Benthic Alonella nana was dominant at that time. After that, probably during the Boreal and early Atlantic periods, Cladocera species diversity increased and planktonic forms (bosminas) became dominant, pointing to a rise of water level. The species composition indicates that the lake was meso- to eutrophic. The lake began to shallow during the middle Atlantic. The process was completed in the Subboreal and the lake transformed into a bog. The fall in water level and fi nally the terrestrialization of the lake is correlated with similar processes recorded in other sediment sequences in northern Poland, suggesting that this event may have been driven by regional factors such as lower precipitation.