Follicular lymphoma is often seen as an indolent disease with a reasonable medium-term survival. We have used the information in the Scotland and Newcastle Lymphoma Group database to devise an index which is easily calculated and differentiates patients into poor, intermediate and good prognostic groups with 5 year survivals of 24%, 61% and 86% respectively. The key factors at presentation are age, ECOG performance status, stage and the presence or absence of B symptoms or gastro-intestinal tract involvement. The use of such an index permits early identification of patients with a poor prognosis for whom more intensive treatment could be offered.