Polyhydroxybutyrate (PHB) can be used as an alternative polymer to polylactide-glycolides for drug carrier production. It is a linear homopolymer biosynthesized by various strains of bacteria by condensation of D(-)-B-hydroxybutyric acid and used as an energy and carbon source. PHB can be obtained by extraction from bacteria or by chemical synthesis. To be suitable as drug carrier the polymer has to be biocompatible, biodegradable in certain applications, and nontoxic. PHB seems to be biocompatible and biodegrades readily to carbon dioxide in bacteria; however, in humans, the reports are few and contradictory. The polymer is nontoxic and its monomer seems to be tolerated well in relatively high concentrations. Possible applications include implants and i.m.-administered particulates for controlled release and i.v.-injected colloidal carriers for drug targeting.