During recent decades the design of modern automotive batteries has undergone a fundamental change from leaf-type separators to microporous polyethylene envelope separation. The increased energy content and higher cold-crank performance of automotive batteries, especially in combination with application at elevated temperatures, has significantly increased the demand on separators with regard to puncture strength and oxidative stability. This paper describes recent achievements, together with typical battery test results, and gives an outlook on probable automotive battery developments from the separator manufacturer's point of view. (C) 2003 Elsevier B.V. All rights reserved.