Background HTLV-1 infection is endemic in Mashhad, Northeast of Iran. This study was designed to assess the epidemiology of HTLV-1 and potential risk factors in Neyshabour, Northeastern Iran. Methods All those who referred to Iranian Academic Center for Education, Culture and Research (ACECR)- Mashhad Laboratory in Neyshabour for evaluation of HTLV-I by ELISA, were tested using WB if the ELISA result was positive. A questionnaire about risk factors of infection was completed for all cases. Results HTLV-1 infection was positive in 7.2% (35/483) of the participants according to the results of enzymelinked immunosorbent assay (ELISA) and western blot (WB) tests. Infection was significantly associated with age, family size, income and blood transfusion. However, gender, education, birthplace, race, marital status, and history of surgery, dentistry, traditional cupping, and hospitalization showed no significant relation. Conclusion It seems that HTLV-I infection is highly endemic in Neyshabour and it is seems that more effective treatment strategies are needed.