Human T-lymphotropic virus (HTLV) infection is rare in the United Kingdom (UK) and few studies are available worldwide. Following introduction of blood donation testing in 2002, a cohort of individuals could be identified and prospectively recruited to describe progression and onset of disease. Here we describe baseline characteristics of participants, and evaluate recruitment into the UK HTLV National Register over the first six years, from July 2003 to June 2009. A multicentre cohort study recruited participants from the UK blood services (recipients and donors) and specialist HTLV clinics. Almost half of the 148 participants recruited were blood donors, nine were blood transfusion recipients, 40 contacts and 29 clinic attendees (nine asymptomatic and 20 symptomatic). Most participants were HTLV-1 positive (n=115); 11 had HTLV-2 and 22 were HTLV-negative. Baseline self-completion questionnaires were received for 83%. The most commonly reported condition was a past operation/serious illness (69%). Twenty-six participants reported four or more possible signs/symptoms of HTLV-1-associated myelopathy/tropical spastic paraparesis. Recruitment into a study of a rare, long-term infection is challenging. This cohort will enable descriptions of HTLV-associated disease progression amongst people recruited from varying sources; it is the first prospective study of its kind in Europe.