The chimeric monoclonal anti-GD2 antibody ch14.18 is made up of the variable region of the murine anti-GD2 antibody 14.18 (or its IgG2a switch variant 14G2a) and the constant region of human IgG1k. Ch14.18 mediates antibody dependent cytoxicity and complement dependent lysis in vitro. In a phase 1 trial, 13 patients with metastatic melanoma received ch14.18 as a single dose of 5–100 mg. Therapy was associated with an infusion-related abdominal/pelvic pain syndrome, which required intravenous morphine for control. The pharmacokinetics of ch14.18 best fit a two-compartment model with a T1/2α of 24±1 hr and a T1/2β of 181±73 hr. Eight of 13 patients developed a weak-modest antibody response directed at the variable region of ch14.18. Clinical antitumor responses were not observed at the doses employed in this study. However, patients receiving >45 mg of ch14.18 had antibody detectable on tumor cells analyzed by fluorescent activated cell sorter. Further modification of the therapeutic regime employing larger doses and frequent administration of ch14.18 are planned. © 1992 Butterworth–Heinemann.