Spore populations of the 35 Streptomyces strains, representing 23 of major phenotypic clusters (Williams et al. 1989), were tested for their viabilities when treated wiht 1.5% phenol at 30 องศา for 30 min (Table 1). Spores of the S.violaceusiger-cluster (no.16) strains were found to be resistant to phenol,in which 10-80% of the spore populations survived.Conversely, spores of strains belonging to other phenotypic clusters appeared to be killed by the treatment,except for the S.albus IFO 3418 spores,which were resistant to phenol.