Thirty-two nonmetastatic melanoma patients with low T-lymphocyte values were treated with a thymic extract, thymostimulin (TS) (8 patients), DTIC (8 patients), or surgery alone (16 patients). In the 8 patients receiving TS, active E-rosette (T-Ea) and total E-rosette (T-Et) counts rose to normal levels and there was a significant rise in IgM and IgD receptors. Six out of eight patients treated with TS showed no evidence of metastases after 34 months, while 7/8 patients on DTIC and 13/16 patients on surgery alone developed metastases. Twenty metastatic patients with low T-lymphocyte values received either DTIC plus TS or DTIC alone. Total lymphocyte, T-Ea, and T-Et counts did not increase in either group nor was there a significant difference between the group on DTIC plus TS and the group on DTIC alone. The survival rate of patients on DTIC plus TS did not differ significantly from that on DTIC alone.