The development of HTLV-1-associated myelopathy (HAM/TSP) in HTLV-1-infected individuals is probably a multi-factor event, in which the immune system plays a crucial role. The efficiency of the host immunity seems to be one of the in vivo determining factors of the proviral load levels and is regulated by genes associated with MHC class I alleles (HLA). Protection or predisposition to HTLV-1-associated diseases according to individual HLA profile was shown in Japanese studies. The present work tested for HLA alleles previously related to protection or susceptibility to HTLV-1-associated myelopathy in a cohort study (GIPH) from Brazil. A total of 93 HTLV-1-infected individuals participated in the study, as follows: 84 (90.3%) asymptomatic and 9 (9.7%) with HAM/TSP. Alleles related to protection (A*02, Cw*08) and susceptibility (B*07, Cw*08 and B*5401) were tested by the PCR-SSP method. Allele A*02 was more frequent in the asymptomatic group and in its absence, Cw*07 was correlated with HAM/TSP (P = 0.002). Allele B*5401 was not present in the Brazilian population. Alleles B*07 and Cw*08 were not different between the groups The presence of HLA-A2 elicits a stronger cytotoxic response, which is involved in the HTLV-1 proviral load reduction. This study confirmed a tendency of this allele to protect against HAM-TSP. Therefore, A*02 might be of interest for researches involved with HTLV-1 vacine