Three representative lead oxides were used in fabricating lead‐acid cells with pure and antimonial lead grids. The cells were cycled and overcharged. Positive plates were removed at intervals and the active material was examined by x‐ray diffraction, electron microscopy, and by spectroscopy. Bulk densities of the active materials were also determined. The cells with pure lead grids usually had somewhat lower capacities than the corresponding antimonial cells, and lost approximately 80% of their initial capacity between 5 and 10 cycles. None of the antimonial cells suffered major capacity loss during the 21 cycles comprising the test. The rate of loss in bulk density of the was higher in the pure lead cells. This and the loss in capacity have been attributed to the grain growth and anhedralization that take place more rapidly when antimony is absent. Antimony appears to act as a nucleating catalyst for the and inhibits crystal growth.