Lymphocytes from 25 healthy donors were separated into T‐ and non‐T‐fractions by means of E and EAC rosette‐formation. The unfractionated lymphocyte population was tested simultaneously with E and non‐EAC rosette‐forming cells (T‐cells) and EAC and non‐E rosette‐forming cells (non‐T cells) on melanoma cells from cell lines and short‐term cultures. More frequent and stronger cytotoxic effects were seen on melanoma target cells from cell lines than from short‐term cultures. The cytotoxic effects of the unfractionated lymphocyte populations were always recovered in the non‐T‐cell populations. Occasionally also T‐cell cytotoxicity was seen on melanoma cells from cell lutes. Compared to the T‐cell effects, the non‐T cells always showed stronger cytotoxic effects. Lymphocytes from selected melanoma patients (patients with known cytotoxic lymphocytes) were also tested tegether with lymphocytes from healthy donors. The cytotoxic effects scored with the unfractionated melanoma patients' lymphocytes, which in general were stronger than the effects seen with the corresponding lymphocyte populations from healthy donors, again appeared to be located mainly in the non‐T‐cell populations.