An osmotic device is disclosed for delivering an active agent. The device comprises a wall surrounding a compartment with a passageway through the wall for releasing the agent. The wall comprises a material permeable to an external fluid and substantially impermeable to agent and at least one additional material independently selected from materials that impart stability to the wall, enhance the permeability of the wall to fluids, or aid in forming the wall. The compartment contains an agent that exhibits an osmotic pressure gradient across the wall against an external fluid, or the agent is mixed with an osmotically effective compound that exhibits an osmotic pressure gradient against the fluid. Agent is released from the device by fluid being imbided through the wall into the compartment at a rate controlled by the permeability of the wall and the osmotic pressure gradient across the wall, thereby producing a solution containing agent that is released through the passageway at a controlled rate over time.