Micron-sized barium sulfate (or barite) particles of various morphologies were prepared via a simple precipitation reaction of sodium sulfate with barium chloride in the absence and presence of poly (styrene-alt-maleic acid) (PSMA) as a crystal modifier at ambient temperature. The as-prepared products were characterized with scanning electron microscopy (SEM) and X-ray diffraction (XRD). The effects of experimental parameters on the crystallization and external morphologies of the as-obtained barite particles were investigated and discussed. The results showed that various morphologies of barite particles, such as flower-like aggregates, spheres, rod-like superstructures, etc. could be synthesized by changing the experimental conditions. It was found that the concentration of PSMA, pH value of solution, and molar ratio of Ba2+ to SO42- (R) were the most important parameters for the morphological control of barite particles. The effects of all these parameters on the morphologies and crystallization of barite can be attributed to their influence on the interaction between the carboxylic acid groups of PSMA and the crystal planes of barite. In addition, this research attempts to provide a preliminary understanding for the formation mechanism of the as-obtained spherical barite particles. (c) 2004 Elsevier B.V. All rights reserved.