Abstract: A portable controlled release osmotic infusion device, which can be activated on demand by the user, comprising a rigid housing containing:a. a fluid-imbibing assembly, comprising a solvent-containing chamber and a solute-containing chamber; the two chambers separated by a rigid semipermeable membrane covered by a thin taut foil seal,b. a drug-containing chamber separated from the fluid-imbibing assembly by a leakproof impermeable elastic diaphragm, which expands into the drug-containing chamber in use and drives the drug through a dispersing orifice at a steady rate, andc. an activating device which ruptures the foil seal described in (a) above and initiates the osmotic action of the device.The osmotic device is filled with drug in solution or suspended form during manufacture and can be stored without deterioration of the contents for prolonged periods of time.