Ciprofloxacin albumin microspheres were prepared by the spray drying technique, with bovine serum albumin as the natural biodegradable wall material. The spherical microspheres, flowed well, were organic solvent free and in the size range 1-5 microm. The drug release from the microspheres could be retarded by further thermal denaturation. The sustained-release microspheres were suitable for dry powder inhaled lung drug delivery systems.