Approximately 3.4 million tons of biosolids, dry weight, are land-applied annually to farms, forests, rangelands, mine lands, and other land use types. Biosolids are defined by the U.S. Environmental Protection Agency (EPA) as "the primarily organic solid product yielded by municipal wastewater treatment processes that can be beneficially recycled" as soil amendments. Concerns for potential human health effects from land-applied biosolids can be addressed through the conduct of a risk assessment. This book focuses on the systematic planning step (a "problem formulation" defining the major factors to be considered) for risk assessments of pathogens in land-applied biosolids. This book follows the common problem formulation steps of hazard identification, conceptual model development, and the development of an analysis plan. A review of pathogens in biosolids literature forms the basis of this book. The intended use of this book is to assist in the development of future risk assessments and to identify specific research needed to fill current data gaps.