A delivery device [(1) in Figure 1a] capable of delivering one or more active substances by diffusion through plural micropores in the membrane (4) or by osmotic pumping through one or more performed passageways (5) in the membrane is provided. The device (1) contains a centrally located expandable core (2) completely surrounded by an active substance containing layer (3), which is completely surrounded by the membrane (4). The device is capable of delivering insoluble, slightly soluble, sparingly soluble and very soluble active substances to an environment of use. The preferred delivery rate is zero order. The device can deliver an active substance for a period of about 12-24 hours.