The appearance of foam on the surface of deep-pit swine manure storages is a serious concern for the pork industry. Manure foam has the capacity to trap gases produced by the anaerobic decomposition of the manure, leading to dangerous flammable gas concentrations upon foam disruption. Field sampling and feeding trials were conducted to determine manure characteristics leading to foam accumulation. Results indicated that foaming pits were more biologically active having lower volatile fatty acid contents and higher rates of methane production. Research is being undertaken to develop foam mitigation strategies based on these findings.