Abstract. . Tribasic lead sulfate 3BS and tetrabasic lead sulfate 4BS , used as precursors of the positive active material in the leadracid batteries, were prepared by a new method: reactive grinding. The effects of various experimental parameters stoichiometry, hygrometry. of the starting compounds, duration of mechanical treatment upon the nature and morphological features of the resulting phase wereinvestigated. Among them, hygrometry turned out to be the most critical one. With water in excess, only 3BS was produced while dryreagents led to 4BS. In both cases, samples with a small particle size and high reactivity were obtained. In order to evaluate the influenceof the morphology upon the electrochemical performances of such grinding produced samples, the capacity was measured and comparedwith that of traditional 3BS and 4BS samples. q1998 Published by Elsevier Science S.A...