Cutaneous T-cell lymphomas (CTCL) represent a heterogeneous group of peripheral T-cell lymphomas arising in the skin and show considerable variations in clinicopathological features. This study was designed to examine viral genomes and cellular proliferation markers in CTCLs arising in Korea. On the basis of their morphologic characteristics and immunophenotypes, 43 cases of primary CTCL were classified, and evaluated for association with either HTLV-I or EBV, p53 protein immunoreactivity and Ki-67 labeling index (LI). EBV was demonstrated in 15 cases (35%) either by EBER in-situ hybridization or PCR; particularly high rates were exhibited by angiocentric T-cell lymphomas. PCR was used to detect HTLV-I proviral DNA, but none was found. The p53 expression rate was higher in large cell lesions, but the Ki-67 LI failed to show any significant differences among the different types. We therefore concluded that in Korea, HTLV-I is less frequently associated with CTCL than in other endemic countries. EBV was found particularly in angiocentric lesions, regardless of cell size or degree of pleomorphism. Because of its high positive rates in high grade lesions, the p53 expression showed positive correlation with histologic grade; however, the Ki-67 labeling index did not correlate with the histologic grade in CTCL.