The type strains of 451 validly described Streptomyces species were screened using the BOX-PCR fingerprint technique. Of the different primers tested, the BOX primer yielded the most robust and reproducible band patterns. The majority of the species (350) had an unique pattern each. A total number of 30 clusters were delineated comprising species with nearly identical patterns. Four of these clusters grouped synonymous Streptomyces species known from previous studies. A high correlation exists between BOX-PCR fingerprinting and DNA-DNA homology data. In the present study, the latter was confirmed for 7 additional BOX clusters and led to the following emended descriptions: S. cochleatus is a subjective synonym of S. cinereorectus, S. roseoflavus of S. fradiae, S. roseodiastaticus of S. tricolor, S. roseosporus of S. filamentosus, S. distallicus of S. colombiensis, S. arabicus of S. vinaceus and S. phaeoviridis of S. phaeopurpureus. Although not yet confirmed by DNA-DNA pairing studies, rep-PCR data suggested the presence of at least 33 additional junior synonyms.