Abstract: A sustained release composition for releasing a biologically active compound into an aqueous liquid environment comprises a biologically active compound dispersed in a matrix which progressively erodes in contact with a liquid environment, the matrix having a melting point below the melting point of the biologically active compound, and the matrix comprising a mixture ofa.) 5% to 100% by weight of a solid water-dispersible polyether diol having a molecular weight from about 1000 to about 20,000, selected from the group consisting of polyethylene glycols and polyethylene oxide-polypropylene oxide block copolymers, andb.) 95 to 0% by weight of an erosion rate modifier which is an amphiphilic compound insoluble in the aqueous liquid.Dosage forms comprising the sustained release composition are prepared by molding, particularly by injection molding.