The tranmission of force to the die wall was measured by a piezoelectric sensor, and the compression cycles of lactose granules of different shapes were compared. In addition, a nearly spherical fraction of spray-dried lactose was similarly compared with a crystalline sample. Better tablets were formed when the conversion of axial to radial pressure was high and the residual pressure on the die wall remained after removal of the top punch. With acetaminophen and phenacetin, the pressure on the die wall was low, as was the residual pressure, and capping occurred in both cases. With direct compression acetaminophen, higher die wall pressure was produced and capping did not occur. It is considered that these results can be explained by the ease with which the more nearly isodiametric particle can rearrange under pressure and by the elastic properties of the solid.