A process of urban decay, coupled with forced displacement and behavio
ral problems, affects an increasing number of neighborhoods in large U
.S. cities. The resulting social disintegration has intensified a nexu
s of deviant behaviors and conditions, including substance abuse, that
are related to transmission of HIV and resurgence of other contagious
diseases. These diseases will diffuse, or are already diffusing, alon
g the transportation hierarchy from larger into smaller central cities
, and radially from the central cities into the surrounding areas. A w
idespread program of urban reform is a critical precondition for the c
ontrol of contagious disease in the United States. It also is importan
t for housing, social services, housing-related public services, and p
ublic health across urban and suburban jurisdictions.