An implantable infusion pump which uses elastomer spring pressure to provide constant-rate drug delivery is described. Desirable features of the design are its low-cost construction, temperature and pressure insensitivity, high volumetric efficiency, and scale flexibility. Test results for prototype models are reported. Spring performance characteristics appear to be unaffected by long-term implantation. The results indicate that the pump is suitable for multiple-drug-delivery applications requiring more than an infusion port but needing a programmable device