Polyurethane microparticles are derived from structural units comprising poly(alkylene oxide) moieties, caprolactone moieties and urethane moieties. The microparticles may include an active agent and have a particle size from 0,1 to 100 microns. Microparticles for injection have a particle size of 15 to 80 microns for use as a aerosol 1 to 3 microns and for intraocular use 0.02 to 2 microns. Dispersivity is in the range 1 to 3.
