In the present study, a total of 290 actinomycetes isolates were obtained from 19 karstic caves in Turkey. Out of these, 131 were chosen for numerical classifi cation studies according to their morphology and pigmentation properties. Representative isolates were compared with the reference Streptomyces strains based on their various taxonomic characteristics such as biochemical, physiological, nutritional, and morphological, totalling 134 unit characters. Th e data were evaluated using simple

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... tching coeffi cients (S SM ), and clustering achieved using the Complete algorithm by X-Taxon and NTSys-pc programs. Th e test strains were assigned to 9 major (5-11 strains), 18 minor (2-4 strains), and 31 single membered clusters. As an encouraging result, all cave isolates tested in the present study were grouped in diff erent clusters from reference Streptomyces strains except for 4 of them. Th is is the fi rst report concerning the distribution of actinomycetes in karstic caves in Turkey.