A portable pump, useful for medical and non-medical uses, has two pouches (3, 4) in pressure transmitting relationship, the first (4) containing an infusate (5) and the second (3), a driving medium (2). The driving medium is pressurized in any of a variety of ways, including activation of osmotic pump, electrochemical reaction (19), release of pressurized fluid or gas (21, 23) or mechanical means (24). The rate of infusion is controlled by a rate controller (18). The infusate pouch is separately manufactured and can be stored apart of the rest of the system. Pulses of pumped fluid can also be delivered according to one aspect of the invention (18, 40).