This paper, one of a series of articles addressing mortgage markets in the year 2000, analyzes structural change in mortgage markets and derives their implications for providing access to homeownership.  In recent decades, the housing finance system has been transformed.  Today, the secondary mortgage market is the dominant source of funds for long-term residential mortagages.  This is a major change from traditional reliance on the thrift industry as portfolio lenders.  The author examines the evolution of the housing finance system and projects current trends to predict the structure of mortgage and housing markets in the year 2000.  This report also addresses the limited ability of the housing finance system to assure access to affordable homeownership and the remaining role of the government.