A new method for the isolation of CD56+ lymphocytes from peripheral mononuclear blood cells is described. Magnetic microbeads conjugated to goat antimouse antiserum in combination with a murine monoclonal anti-CD56 antibody were coated to the CD56+ target cells. CD56+ cells were then isolated with the use of a magnetic cell sorter. The purity of the CD56+ cells was 98.4 +/- 1% (n = 12) with a recovery of the CD56+ lymphocytes of 57.2 +/- 9% (range 48-77%). The natural killer, activity of the CD56+ lymphocytes as well as the interleukin-2-induced proliferative response were not affected by the isolation procedure or the presence of the magnetic microbeads on the CD56+ cells. The described method might be a useful tool for the further characterization of CD56+ cells and their subsets and can easily be upgraded for clinical use in adoptive immunotherapy with CD56+ lymphocytes.