Variation within the intergenic spacer(IGS) of the ribosomal DNA gene for twenty-two strains of E. oxysporum and its formae speciales was examined by PCR, couped with RELP analysis. The length of the amplified IGS region was about 2.6 kb in all strains except F.oxysporum f. sp. cucumer-inum from Korea and F. oxysporum f. sp. niveum. Those two strains were 2.5 kb long. Restriction digestion of IGS-RELP regions by Eco RI, NruI, HincII, SAlI, SmaI, BalIi, HindIII, XhoI and KpnI gave rise to nine IGS hapoltypes among all strains. Cluster analysis based on the presence of absence of comigrating restriction reagments show the two groups based on 44% genetic similarity. These results demonstrated that analysis of IGS showed some difference within and between F. oxysporum formae speciales.