Winter management practices involving the use of stand-off pads to reduce problems due to cows grazing on wet soils may require storage of cow manure for extended periods prior to field application. Gaseous losses of nitrogen (N) and sulphur (S) from stored cow manure can be considerable, and these gases are offensive and undesirable. Laboratory incubation studies were conducted to measure gaseous loss of ammonia (NH3) and hydrogen sulphide (H2S) from stored cow manure under aerobic and anaerobic conditions. The potential of adding a range of natural materials, including soil, untreated pine bark, sawdust and wood savings, to the manure to reduce these gaseous emissions was investigated. Aerobic incubation of manure resulted in a higher emission of NH3 than anaerobic incubation, while anaerobic incubation resulted in higher emissions of H2S. The effectiveness of natural materials in reducing losses of NH3 was investigated under anaerobic conditions, and pine bark was found to be the most effective. However, all materials reduced NH3 to some degree. Therefore, the addition of natural materials, such as pine bark and soil, as amendments to cow manure during storage offers potential for reducing emissions of NH3 and H2S.