Among the many factors that determine and i.~:fluence the performance of lead/acid batteries, one of the most important, and as yet not fully developed, is how to make the positive active ~ass more electrochemically reactive. The inherent characteristics of this active mass ate the cumulative result of the four precursor stages of it~ production, namely, the leady oxide, paste mixing, curing and formation procedures. There is evidence to suggest that the method of pasting ~,self is also influential. Many recent studies have reported progress on techniques to increase active-material utilization, to improve plate condk~oning, and to solve the vexagious problem of premature capacity loss. The purpose of this discussion is to focus attention on the mle and the importance of leady oxide on battery design and performance. At present, the haV.ery industry makes leady oxide by either the ball-mill or the Barton-pot process. It is difficult to conclude which of the two methods gives the best leady oxide. Each type of leady oxide has its champions but, in general, ball-mill and Bartun-pot product both make effective automotive batteries. For deep-cycle batteries, however, many battery compaMes (especially in Europe and Japan) prefer hall-mill oxide; in Nm'th America, the Barton-pot variety is favoured. This investigation examines the present procedures for making leady oxide, the desirable properties of leady oxide, and the influence of the oxide on battery pedormance. Analysis shows that there is scope for the production of improved leady oxide --by using existing production techniques aud/or by the development of new processing technology.