Homeless persons have always been present in the United States, but their numbers have increased substantially in the 1980's. Most housing experts agree that the leading cause of homelessness is the lack of affordable housing. Both the private sector and the government have taken action to aid the homeless. The McKinney Homeless Assistance Act is the center of Federal efforts on the issue. However, it has not been fully funded. Options under discussion for future action include full funding of the McKinney Act, increased housing production and rehabilitation, programs to prevent evictions and foreclosure, the provision of selective sanctuary for mentally ill homeless persons, changes in rent control laws, replication of model programs, and wider use of housing vouchers. Reference notes.