AbstractA new class of pharmaceutical dosage forms—therapeutic systems—has been developed. Unlike conventional dosage forms (i.e., pills, capsules, or sustained release preparations), which are specified only by the amount of drug they contain, therapeutic systems are described both by the rate and duration of drug delivery. The first products to embody this technology are: (1) an ocular therapeutic system that delivers the anti‐glaucoma drug, pilocarpine, to the eye for one week; (2) an intrauterine contraceptive system that delivers the fertility controlling hormone, progesterone, to the uterus for one year; and (3) an oral osmotic delivery system for administration of drug to the gastrointestinal tract. Specific furictiQns of polymers as constructional elements of therapeutic systems are discussed and consideration is given to properties critical to the intended performance, test procedures, and parameters for prediction of mechanical and physico‐chemical functionality, stability, and