The human genome contains a large number of endogenous retroviruses (HERVs). Their reactivation has frequently been observed in patients with cancer. Considering their role in the carcinogenesis process, we aimed to study the possible relationship between HERVs gene expression and Chronic Lymphocytic Leukemia (CLL). We focused on two viral genes gag and np9, the latter presumably an oncogene. We found that the transcriptional activity of HERV-K np9 gene was greater in CLL patients than in healthy donors. However, gag expression was not significantly increased. These findings suggest a noteworthy relationship between CLL disease and HERV-K np9 expression.