One hundred twenty-four patients with metastatic malignancy were treated with four different single agent infusion programs by constant intravenous infusion for 30 or more days. Drug was administered via a tunneled subclavian line by a battery-driven peristaltic pump (Cormed model ML6) on an ambulatory basis. This schedule allowed for increased cumulative drug dose for 5-Fu, decreased tolerated dose for vinblastine, and comparable doses for adriamycin and mitomycin-C relative to that delivered with the standard intermittent bolus schedule. Therapeutic effects were observed for three of four drugs studied: 5-Fu 13/31 colorectal cancer; adriamycin 7/29; and vinblastine 4/12, including 2/4 melanoma. Adverse effects were significantly reduced, particularly with regard to gastrointestinal toxicity, but also in adriamycin-associated cardiac effects and hair loss. Phase III comparative trials of intermittent bolus therapy with protracted infusion therapy are in progress for 5-Fu in advanced colorectal cancer and for adriamycin in specific tumors. Ambulatory pump infusion (API) chemotherapy is technically feasible and has improved patient tolerance to chemotherapy while demonstrating similar, if not comparable, antitumor effects.