To present the first documented case of human T-lymphotropic virus type I (HTLV-I) associated myelopathy/tropical spastic paraparesis in the Australian population. A 31-year-old Aboriginal man with an 18-month history of progressive weakness of the legs was found to have an upper motor neurone weakness of all limbs associated with sphincteric disturbance and impotence. HTLV-I antibodies were detected in his serum and no other cause for the patient's myelopathy could be found. He was counselled regarding HTLV-I associated myelopathy/tropical spastic paraparesis. This is the first description of HTLV-I associated myelopathy/tropical spastic paraparesis in an Australian. In cases of spinal cord disorder without evidence of compression we recommend serological testing for HTLV-I, especially in Aboriginal patients. Additionally, testing of blood donors for this retrovirus needs consideration.