An osmotic device for delivering an active agent is disclosed. The device is comprised of a wall surrounding in at least a part, a reservoir containing agent. The wall is formed of a material permeable to an external fluid and impermeable to agent. The reservoir is formed of a microporous material permeable to agent and fluid, and having at least one micropore that is a passageway for release of agent. The agent is soluble in the fluid and exhibits an osmotic pressure gradient against the fluid, or the agent has limited solubility in the fluid and is admixed with an osmotically effective compound soluble in fluid that exhibits an osmotic pressure gradient against fluid. In operation, agent is released by fluid permeating through the wall into the reservoir producing a solution of agent or a solution of compound containing agent, which solution in either instance is released through the micropore to the exterior of the device.