We have previously reported studies performed both in vitro and in laboratory animals, as well as a case study in humans, suggesting that intravenous immunoglobulin (IVIG) may be beneficial in the treatment of malignancies, including metastatic melanoma. As part of a phase II open label trial, we have administered IVIG to nine patients with metastatic melanoma who had been heavily treated. In two of nine (22%) patients treated every 3 weeks with IVIG (1 g/kg body weight), the disease stabilized. One patient had stable disease for 8 months; the other for 3 months. No serious adverse events (AEs) attributable to IVIG were observed. We conclude that IVIG therapy may be useful for the treatment of metastatic melanoma. Furthermore, we suggest that the effects of IVIG therapy might be enhanced by its use as an adjuvant in patients without evidence of disease following surgery.