Fifty-seven adult patients receiving chemotherapy were treated with a total of 133 infusions using portable user-worn infusion pumps, the Autosyringe AS*2F Cormed ML6-4, and two earlier versions of the latter, the Sigmamotor ML6-2 and ML6-3. Ninety-eight infusions were given on an ambulatory basis. Fourteen infusions were given through peripheral venous catheters, 115 through central venous catheters, and four intra-arterially. Of 127 evaluable infusions, 65 were completed within 5% and 87 within 10% of the planned rate; results are similar for both inpatient and outpatient infusions. The Cormed ML6-4 pump was equal to the Autosyringe AS*2F in reliability but superior to the latter in patient preference. There were no instances of dangerously rapid administration of the drug. The only serious catheter complications were a pneumothorax after insertion of a subclavian catheter in one patient and cellulitis in a leukopenic patient with a Broviac catheter. All but three patients preferred outpatient therapy to hospitalization. Outpatient therapy costs about $300 per day less than in-hospital treatment.