Abstract: An osmotically driven fluid dispenser that is capable of being miniaturized and used as an implant to administer fluid drug compositions to animals and humans. The dispenser comprises a flexible inner bag adapted to contain the drug composition, a fluid tight plug fitted into the bag opening, a port in the plug through which the composition may be charged to the bag, an intermediate layer of an osmotically effective solute composition partly covering the bag exterior such that a band of the bag exterior proximate to the plugged end is not covered by the layer, an outer shape-retaining semipermeable membrane covering the layer of solute and forming a fluid tight seal at said band, and a tube that fits snugly through the port in the plug and extends substantially into the interior of the bag after the drug composition is charged to the bag, said tube providing an outlet through which the drug composition may be dispensed.