Lindeman's ( 1942) paper on trophic-dynamic aspects of ecology ignited interest in ecological relationships at the ecosystem level. The development of high-speed computers enabled ecologists to analyze complete ecosystems and to model them (Van Dyne 1966). These interests and activities have culminated in the International Biological Program (IBP) Analysis of Ecosystems. The primary objective of the Analysis of Ecosystems portion of the IBP is to understand the basis of productivity worldwide. This bulletin deals with herbage dynamics and primary production of a desert grassland ecosystem. Primary production is important in any ecosystem; it fuels consumer and decomposer groups. Products from primary production also influence abiotic parameters. Litter on the soil surface influences infiltration rates and, as it is incorporated into the soil, changes physical and chemical soil properties. Many studies have been concerned with desert grassland vegetation and have analyzed end-of-season standing crop of certain groups of plant species, but few have analyzed the details of herbage dynamics, primary production, and energy dynamics of primary producers under desert grassland conditions.