Background: Because of the low prevalence of Human T Lymphotropic Virus type I (HTLV-I) in comparison withKhorasan Province, considering HTLV-I as an etiology of spastic paraparesia, it may be neglected in evaluationof spastic paraparesis in the other regions of Iran. Some reports of spastic paraparetic patients due to HTLV-Iinfection in West Azarbaijan, caused us to reconsider the importance of HTLV-I epidemiology in the other areasof the country.Methods: All spastic paraparetic patients who referred to Motahari and Imam Khomeini educational hospitals ofUrmia from September 2004 to September 2007 were assessed for HTLV-I infection antibodies.Results: In our 3 years study, 11 cases were diagnosed as Human T Lymphotropic Virus type I AssociatedMyelopathy/Tropical Spastic Paraparesis (HAM/TSP, 2 males and 9 females).The mean age of patients at thetime of diagnosis was 45.8 years. Dorsal and cervical MRI of all patients was normal. Serum Enzyme-LinkedImmuno-Sorbent Assay (ELISA) and Western blot (WB) for anti HTLV-I antibody in all patients was positive. Fourpatients underwent for lumbar puncture in which were normal in respect of cells and biochemistry, but positive foranti-HLTLV-I antibodies.Conclusion: HAM/TSP detection in West Azarbaijan in spite of its long distance from Khorasan Province showsthe importance of anti-HTLV-I Ab assay in the blood and CSF of every spastic paraparetic patient all over thecountry.