Antimonial lead alloys continue to play a key role in the overall success of the lead-acid battery in deep cycle applications. In markets such as motive power and golf car, these alloys have long been known to assist the performance of the positive plate by promoting a healthy, grid-active material interface. Antimony, on the other hand, is a well-established poison to the negative plate and ultimately leads to gassing, water-loss and cell failure. Reports in the literature indicate that specific battery separator materials may be used to delay the onset of gassing by suppressing the effects of antimony. Literature findings also suggest that the suppression effect may be due to a combination of the chemical make-up of the separator and its physical attributes. It is the intention of this paper to introduce a novel method for evaluating battery separator materials in terms of their ability to suppress the deleterious effects of antimony. Results presented here indicate that the chemical composition of the separator is a controlling factor in suppressing the influence of antimony in the lead-acid battery. Initial information on the characteristics of a new hybrid rubber-polyethylene battery separator is also presented.