One of the oldest forms of financial regulation in the United States is the usury law. At the present time there are statutes governing the maximum allowable interest rate which a lender can charge an individual on a residential home mortgage loan in all but five states. These statutory rates vary appreciably among the states ranging from a low of 7-1/2 per cent in New York, New Jersey, and Vermont to a high of 21 per cent in Rhode Island. During recent years, usury limits in many of the states have remained inflexible in the face of rising market interest rates. As shown in Table I, sixteen states and the District of Columbia had general usury limits on home mortgage loans of eight per cent or less during 1970. This was below prevailing mortgage rates for the nation as a whole. Although a number of the states, particularly those with lower ceilings, exempt FHA and VA mortgages from the statutes, there is a Federal limit imposed on such loans which is generally below prevailing mortgage rates as well. However in 1970, when the FHA-VA ceiling rate was 8-1/2 per cent, usury limits in states like New York were a full percentage point below the Federal limit. The purpose of this paper is to investigate empirically the relation between "unduly low" usury ceilings and the level of single family homebuilding. Using cross section data for a sample of 77 Standard Metropolitan Statistical Areas (SMSAs) for the year 1970, a model is constructed which relates the quantity of single family housing starts to a number of important economic and demographic determinants including real per capita income, population levels, population growth, population density, housing prices, and a dummy variable measuring the impact of low usury ceilings. The model is estimated using ordinary least squares techniques and the results indicate that in SMSAs where statutory rates lie below market rates, the level of single family home-building is, on average, approximately 28 per cent lower ... [ABSTRACT FROM AUTHOR]