Broad phase II trial of methylglyoxal-bi (guanylhydrazone) (MGBG) is under way at the Memorial Sloan-Kettering Cancer Center. Studies in renal cell carcinoma, lymphomas, and non-small-cell lung cancer are completed, and substantial numbers of patients with esophageal and head and neck cancer have been treated. Small numbers of patients with other solid tumors have also been entered into the study. MGBG has significant antineoplastic activity against lymphomas, with 16/40 heavily pretreated patients (40%) having partial remissions (PR) lasting 1 to 8+ months. MGBG has also demonstrated more modest activity in non-small-cell lung cancer, esophageal, and head and neck carcinoma; it appears to have little or no therapeutic value in renal cell cancer. Toxicities have been manageable, and included mild nausea and vomiting, diarrhea, mucositis, and myelosuppression. The dose-limiting toxicity, seen most frequently in those patients with impaired renal function, was lethargy and fatigue. MGBG has demonstrated activity in lymphomas, lung, esophageal, and head and neck cancer. Further trials of this agent are indicated, both alone and in combination.