A set of 18 Y-chromosomal microsatellite loci was analysed in 568 males from Poland, Slovakia and three regions of Belarus. The results were compared to data available for 2,937 Y chromosome samples from 20 other Slavic populations. Lack of relationship between linguistic, geographic and historical relations between Slavic populations and Y-short tandem repeat (STR) haplotype distribution was observed. Two genetically distant groups of Slavic populations were revealed: one encompassing all Western-Slavic, Eastern-Slavic, and two Southern-Slavic populations, and one encompassing all remaining Southern Slavs. An analysis of molecular variance (AMOVA) based on Y-chromosomal STRs showed that the variation observed between the two population groups was 4.3%, and was higher than the level of genetic variance among populations within the groups (1.2%). Homogeneity of northern Slavic paternal lineages in Europe was shown to stretch from the Alps to the upper Volga and involve ethnicities speaking completely different branches of Slavic languages. The central position of the population of Ukraine in the network of insignificant AMOVA comparisons, and the lack of traces of significant contribution of ancient tribes inhabiting present-day Poland to the gene pool of Eastern and Southern Slavs, support hypothesis placing the earliest known homeland of Slavs in the middle Dnieper basin.