The properties of different forms of carbon and their potential, as active mass additives, for influencing the performance of valve-regulated lead–acid batteries are reviewed. Carbon additives to the positive active-mass appear to benefit capacity, but are progressively lost due to oxidation. Some forms of carbon in the negative active-material are able to resist the tendency to sulfation during high-rate partial-state-of-charge operation to some considerable extent, but the mechanism of this benefit is not yet fully understood.