This report addresses solutions to problems of fungus growth on library materials. The first of four sections--"What Is Mold? Where Does It Come From?"--defines mold, mildew, and fungi, and describes their optimum environment (i.e., generally in conditions with temperatures above 70 degrees and relative humidity above 78%). The second section--"What Does Mold Do to Books and Paper, and to People?"--discusses some effects of fungi such as mold and mildew, including: (1) an increase in the rate of book and paper deterioration by accelerating the aging process and the formation of acids; (2) mold and mildew stains that destroy text and images; (3) a weakening and softening of books and paper, making them difficult to handle; and (4) adverse effects on human health. The third section--"The Repulsion of the Giant Spore, or How To Rid One's Collection of Mold"--makes up the greater part of the report. It prescribes methods for inhibiting the growth of or killing fungi, with emphasis on nontoxic, nonchemical environmental control measures for both prevention and cure. Other nonchemical (e.g., freezing, gamma radiation, and ultraviolet light) and several chemical (i.e., fungistatic and fungicidal) treatments are also detailed. The fourth section--"Concluding Recommendations"--advises that fumigating collections with toxic or hazardous chemicals is rarely necessary for dealing with mold and mildew problems, and provides a checklist to consult before instigating chemical treatments. (29 references) (SD)