Lymphocytosis of large granular lymphocytes (LGL) has been observed in 6 patients splenectomized for various pathological conditions. In all of them the LGL count was higher than 3.5 x 10(9)/l. No patient showed neutropenia nor suffered from rheumatoid arthritis. A surface markers heterogeneity was observed by immunophenotypic studies. A reversal of the CD4/CD8 ratio was observed in all patients, indicating that LGL are in the majority CD8+. Three patients showed the phenotype CD2+ CD3+ CD4- CD8+ indicating the T-lineage derivation of LGL; patient 6 showed a non-T non-B phenotype (CD2- CD3- CD4- CD8+/-). The percentage of lymphocytes presenting LGL-related markers (HNK-1, CD16, CD11b) was higher than that observed in normal subjects in 4 out of 5 examined patients. However, the percentage of cells bearing these markers was inferior to the LGL counts indicating that not all LGL express them. NK cytotoxic activity was similar to that of normal subjects in the three examined patients. Our data suggest that lymphocytosis of LGL in splenectomized subjects is a reactive process favoured by the asplenic state.