The National Cancer Institute of Canada Clinical Trials Group undertook a phase II study of 2'-deoxycoformycin in patients with metastatic renal cell carcinoma. When 2'-deoxycoformycin 4 mg/m2 was administered intravenously weekly for three weeks then every two weeks no significant antitumor activity was noted in 19 evaluable patients. Toxic effects experienced were as expected, consisting primarily of nausea/vomiting, anorexia, and lethargy. It is concluded that 2'-deoxycoformycin at this dose and schedule has no clinical activity in the treatment of metastatic renal cell carcinoma.