A method for preparing particles suitable for pulmonary drug delivery by inhalation, and inhalation compositions comprising such particles are provided. The method comprises providing a liquid feed stock comprising one or several active agents, atomising the liquid feed stock, suspending the droplets in a carrier gas, and passing the carrier gas and droplets through a heated tube flow reactor under predetermined residence time and temperature history, and collecting the particles produced. Fine uniform crystalline spherical uncharged particles with narrow aerodynamic particle size distribution between about 1 to 5 mum and rough surfaces, are obtained. The particles show improved dispersibility and stability.
