Peripheral T-cell lymphomas (PTCL) account for approximately 10% of all non-Hodgkin's lymphomas. The aim of this retrospective study was to analyse the presentation, management, outcome and significant prognostic factors in a large series of patients with PTCL. It includes 104 consecutive patients who presented to the Sheffield Lymphoma Group between 1977 and 2001. Clinical parameters were recorded for each subgroup. End points were response to treatment and survival. Survival analysis was used to assess the prognostic value of the variables. PTCL not otherwise specified contributed 52% of cases followed by anaplastic large cell lymphoma with 17% and angiocentric type with 13% of cases. The overall complete remission (CR) of the series was 59%. Stage at diagnosis affected response to treatment with 81% of cases in stage 1 and 2 achieving CR compared to 43% in stages 3 and 4 (p</=0.001). Extranodal presentations also showed a favourable response with 74% obtaining CR compared to 46% of nodal presentations (p<0.01). Median survival of all patients was 87 months with a five-year probability of survival of 52%. Variables found to be related to poor outcome are age >60 years (p<0.05), high grade histology (p<0.001), presence of B symptoms (p<0.005), nodal presentation (p<0.005) and advanced stage at diagnosis (p<0.001). Histological sub-type did not significantly correlate to outcome. In conclusion whilst a number of prognostic indicators can assist in determining the outcome in PTCL, these lymphomas are complex and often follow an unpredictable course. In order to make the best clinical decisions in individual cases, more clinical study is required.