This volume presents a preliminary analysis of the data accumulated thus far in the largest controlled social experiment ever undertaken, the Seattle, and Denver Income Maintenance Experiments (SIME/DIME). The concept of social experimentation is itself not new; modes of organizing for public welfare and distributing benefits and services within communities are virtually always first attempted on a small scale prior to their broader implementation. This research was designed to assess the social and economic impacts of a welfare system based on the principle of a negative income tax.