The Housing Assistance Supply Experiment was designed to learn what effects a full-scale housing allowance program would have on local housing markets in two experimental sites: Brown County, Wisconsin, and St. Joseph County, Indiana. The program tested effects in three major areas: housing prices, neighborhood change, and transactions between participants and market intermediaries. Halfway through the five-year experimental period, the impact of the program was found to be minor in each department. Although both rents and home prices did rise rapidly in each site, virtually all the increases were accounted for by general inflation. While no major contradictions to the interim findings are expected, the conclusions presented here will be further tested, refined, and expanded by additional analysis.