Of actinomycetes isolated from volcanic compost soils, 115 representative strains which showed distinctive morphologicla features were numerically classified, compared with reference strains of Streptomyces. One hundred and twenty unit characters were tested and the average probability of error was 4.27%. The cluster analysis resulted in two groups: group A included strains of actinomycetes except streptomycetes. Group A was divided into 2 major clusters (over 5 strains), 10-diaminopimelic acid. Group B was divided into 5 clusters, of which 4 clusters contained mesodiminopimelic acid and 1 cluster LL-diaminopimelic acid. The major clusters of group A showed higher abilities of substrate utilization and degradation, and higher resistance to inhibitors, whereas the minor and single member clusters of group A showed relatively higher antimicrobial activities. On the other hand, all clusters of group B showed relatively lower abilities of substrate utilization and degradation and lower resistance to inhibitors.