DNA topoisomerases have been evolved to solve the topological problems of DNA during replication, transcription, recombination and segregation. Discovery of several new enzymes and their characterization has necessitated this compilation. This analysis shows the distinct evolutionary relatedness of type II DNA topoisomerases. A striking feature is the absence of a contiguous stretch of about 160 amino acids in one of the subunits of prokaryotic type II enzymes, which might have important implications to their structure and function.