Abstract: An osmotic drug (or other beneficial substance) delivery system comprises a multi-chamber compartment formed by an external shell and one or more chamber-dividing walls each with a small orifice, of a microporous material and overlayers of semipermeable membranes completely covering the outer shell of all but one chamber and substantially covering the outer shell of the remaining chamber. Osmotic agents, adjuvants, enzymes, drugs, pro-drugs, pesticides and the like are incorporated in the chambers covered by the semipermeable membrane, and external fluids that diffuse into those chambers form solutions and by osmotic pressure are forced through the orifice to the drug chamber to form a solution thereof and then through the exposed microporous shell to the exterior of the device at a rate controlled by the permeability of the semipermeable overlay and the osmotic pressure gradient across the shell.