The active mass (AM) utilization is a key factor limiting the specific energy and performance of lead-acid batteries. In this paper, the distributions of AM utilization on two kinds of positive plates have been studied by measuring their local discharge curves. With the discharge of the positive plate, the current density decreases gradually in the lower and upper parts while it increases in the middle. As a result, the distributions of AM utilization are uneven on the positive plate. The highest AM utilization is located in the middle, and the lowest AM utilization is around the plate. Compared with a positive plate with an orthogonal grid, the positive electrode potential increases by 10-50 mV in most parts of a positive plate with a radiation grid at high discharge rate (3C). The positive plate with a radiation grid is more suitable for the application at high discharge rates. © 2005 The Electrochemical Society. [DOI: 10.1149/1.1914749] All rights reserved.