Marine bacterioplankton play important roles in biogeochemical cycles in coastal regions of the sea. Despite its ecological importance, the composition of bacterioplankton community of coastal Black Sea, a unique marine basin in the World, is poorly characterized Thus. the aim of this study was to analyze the bacterial communities in the Black Sea surface waters by terminal-restriction fragment length polymorphism (T-RFLP) analysis, a relatively new, fast and easy molecular method for assessing microbial diversity and community structure. Bacterioplankton assemblages were sampled in shelf surface waters in Constanta Bay between May and August 2004. T-RFLP patterns derived from enzyme digestion with HhaI were analyzed in order to provide a preliminary, picture of the relative diversity of this complex microbial community. Members of both prokaryote domains, Archaea and Bacteria, have been successfully identified using T-RFLP analysis of amplified total community 16S rDNA from surface seawaters and were related to the environmental conditions. A minimum of 20 operational taxonomic units (OTU) were identified with T-RFLP. This study contributes to the evaluation of the Black Sea bacterioplankton diversity and it was used for the first lime in Romania.