The effect of granulation particle size on the weight variation of compressed tablets was studied, using statistical quality control procedures. Batches of lactose-starch granulation particles ranging in size from 3,045 to 324 microns and separated into narrow-size ranges were compressed in a single-punch tablet press. As the particle size decreased, the tablet weight variation decreased, passed through a minimum at 400 to 800 microns and then increased. Data from a somewhat similar experiment involving sodium chloride was found to give a minimum at 200 to 500 microns.