Describes the selection of a stratified probability sample of approximately 4,300 residential properties in St. Joseph County, Indiana, Site II of the Housing Assistance Supply Experiment. Beginning in November 1974, these properties were scheduled for baseline surveys to gather information about each property, its occupants, and its owners immediately prior to commencement of HUD's experimental housing allowance program for low-income families there. A permanent panel of properties was chosen from those with adequate baseline records. Each property in the permanent panel was resurveyed annually for the duration of the experiment. These surveys provide most of the data needed to analyze the effects of the allowance program on the local housing market.