understanding of the slagging and fouling process has developed, how changes in the utility sector have impacted on the importance and likelihood of ash deposition incidents, and how problems may be predicted and tackled on a practical level. Some important factors which impact on the topic are considered in this review including: power generation sector deregulation; technological developments; environmental protection technologies; new technologies; cofiring with biomass and other alternative fuels; increased international coal trading. Developments in the global coal- fired power generation sector continue to influence the subject in a number of ways. Increased competition between utility companies has led to the use of