The purpose of this book is to provide an overview of research on agricultural systems that is both broad and selective. The focus is broad, by covering approaches used in a number of disciplines, as well as in multidisciplinary studies, and by defining agricultural systems to include cropping systems, fanning systems, agricultural household systems, and agricultural systems at higher levels such as the agrarian system. The focus is selective by emphasizing key methods and ongoing debates, rather than attempting a comprehensive review of literature. Most previous reviews of research on agricultural systems have concentrated on a particular approach, eg farming systems research (FSR), including comparisons of anglophone and francophone variants of FSR, or on research conducted in specific geographical settings.