We performed a comprehensive analysis on FHIT gene methylation and expression in uncultured peripheral blood mononuclear cells (PBMC) isolated from healthy volunteer donors (HD), HTLV-I infected asymptomatic carriers (AC), and HTLV-I infected individuals diagnosed with tropical spastic paraparesis/HTLV- I-associated myelopathy patients (TSP/HAM) and adult T-cell leukemia (ATL). Here, FHIT is linked to adult T-cell leukemia/lymphoma.