We reviewed data on 63 patients with mantle cell lymphoma (MCL) with leukaemia (n = 16) and chronic lymphocytic leukaemia (CLL, n = 47), splenectomized over a 10-year period. Primary indications for surgery were cytopenia(s) or autoimmune phenomena and progressive or refractory disease with splenomegaly. The spleens removed were on average larger in MCL (median 2.6 kg) than in CLL (1.0 kg). Splenectomy improved the blood counts in 62% of patients with MCL and 47% with stage C CLL, both with cytopenias. The MCL patients showed a decrease in the leucocytosis (medians 60.3-29.1 x 10(9)/l before and after splenectomy), whereas there was an increase in the leucocytosis in CLL (medians 24.2-44 x 10(9)/l). With a median follow up post splenectomy of 10 months (range: < 1-128), 18 patients (four MCL and 14 CLL) have not required further therapy for up to 66 months. We conclude that splenectomy is a useful treatment in MCL and advanced CLL for the correction of cytopenias, reducing the leucocyte count and allowing prolonged periods of clinical remission without therapy. Differences seen between MCL and CLL in spleen size, and in response of the leucocytosis suggest a central role for the spleen in the evolution of MCL with leukaemia.