Barium and calcium salts of naproxen, (+)-6-methoxy-alpha-methyl 2-naphtaleneacetic acid, were prepared by the controlled double jet precipitation technique in the absence and in the presence of different surfactants. The nature of the latter and agitation used in the precipitation process were critical factors in determining the morphology and the size of the particles obtained, consisting, as a rule, of aggregates of much smaller subunits, which were either platelet or fiber like,