In order to prepare a dry powder inhalation (DPI) formulation for steroid KSR-592, we designed agglomerates consisting of fine primary drug particles suitable for inhalation by the spherical agglomeration method. The agglomerates easily disintegrated into the primary particles and were deposited on carrier lactose particles by use of a conventional agitation mixer in a short period, e.g. 2-10 min. The inhalation behavior of the DPI formulation evaluated with a twin impinger and a cascade impactor in vitro was determined by the mixing time of the agglomerated crystals with the carrier lactose particles. The DPI formulation prepared by mixing for 2 min showed the highest respirable fraction value compared with the formulations mixed for other lengths of time.