Peripheral blood mononuclear cells (PBMCs) from patients with Chediak-Higashi syndrome (CHS) exhibit minimal natural-killer-like cytotoxicity by standard 51Cr-release assays in vitro. However, a CHS-derived γδ-T-cell clone maintained in long-term culture with low-dose interleukin-2 (IL-2) does exhibit cytotoxic activity. PBMCs from 2 patients with CHS were stimulated with low-dose IL-2 in short-term culture and compared with a control for induction of cytotoxicity against a panel of target cell lines. The CHS-derived PBMCs exhibited IL-2-induced cytotoxicity, though the magnitude of induction was uniformly less than in controls. This was accompanied by no significant change in the proportion of PBMCs bearing the γδ-T-cell receptor antigens. The inducibility of cytotoxicity with low-dose IL-2 in vitro suggests a possible in vivo therapy for patients with