The National Association of School Psychologists (NASP) established a policy in 1989 mandating a national study of the field every 5 years. The purpose of the studies was to generate a comprehensive description of the field of school psychology across the United States, as well as to allow for analyses of changes in the field over time. The first study collected data based on the 1989-1990 school year. Subsequent studies were completed every 5 years following the initial study. It has become apparent in the years since adoption of the NASP policy that the data generated through the mandated studies have proven valuable not only to NASP, but to other national and state professional associations, to school districts, and even to individual school psychologists. This article reports the data which reflect the most recent NASP study and are based on the 2009-2010 school year. This article is the first in a two-part series. This report describes the demographic characteristics of school psychologists across the United States as well as the context within which school psychologists work. [For part 2, see EJ981554.] (Contains 2 figures and 2 tables.)