The administration of lymphokine-activated killer (LAK) cells along with interleukin-2 (IL-2) can mediate regression of tumors in selected patients. A closed automated system utilizing commercial blood cell separators has been developed for washing and Ficoll-Hypaque (FH) separation of lymphocytes, for lymphocyte culture in polyolefin bags, and for concentration of LAK cells out of culture prior to infusion. We now demonstrate that preparation of LAK cells can be simplified by elimination of the FH sedimentation step. Patient leukapheresis was performed using Fenwal CS-3000 blood cell separators, with a mean cellular yield per procedure of 54 X 10(9) WBC (95% lymphocytes), 184 X 10(9) RBC, and 306 X 10(9) platelets (n = 22). These cells were then washed in the same apheresis kit with a counter-current flow of saline, thereby eliminating 85% of platelets while retaining 88% of WBC. Aliquots of the washed cells were separated on FH gradients in 50 ml centrifuge tubes, and both FH-separated and washed-only cells were cultured at 3 X 10(6)/ml with 1500 U/ml IL-2 in polyolefin bags. Cytotoxicities of 22 preparations of LAK cells from 14 patients were evaluated in 4 h 51Cr release assays. Cells that were washed-only averaged 47, 35, and 9 lytic units/10(6) cells against K562, Daudi, and fresh tumor, while FH separated cells averaged 46, 33, and 6 lytic units/10(6) cells respectively. Cellular recoveries using the wash-only technique were 25% greater than when using FH sedimentation. Omission of FH separation saves time and expense in preparation and provides greater numbers of LAK cells for use in adoptive immunotherapy.