The objective of this report is to present available information on factors relating to ash fouling and slagging when burning low rank coals in a single reference document to be used by boiler designers, plant operators and coal researchers. The report presents detailed information on coal properties, boiler design and operating experience compiled and organized into two major sections: a plant survey of boiler design and operating data for units over 100 MW at selected US plants burning lignite and subbituminous coal, based on survey questionnaires and data available from the open literature. An interpretive review of factors influencing the occurrence and prevention of slagging and fouling, based on an annotated bibliography dealing specifically with the utilization of low rank coals in utility boilers and related research on coal and ash properties and deposition mechanisms.