This paper examines how unexpected neighborhood changes influence fear
of crime. It focuses on the roles of population composition, signs of
incivility, and unsupervised peer teen groups. Survey, physical asses
sment, and census data for 1, 622 residents in 66 Baltimore city neigh
borhoods form the basis of contextual models of daytime and nighttime
fear levels. Fear was high in neighborhoods experiencing unexpected in
creases in minority and youth populations. Unexpected ecological chang
e does not by itself set in motion a broad array of consequences under
mining neighborhood viability. Rather, ecological change influences ra
cial composition; other structural dynamics, independent of these ecol
ogical changes, subsequently determine the specific consequences of ne
ighborhood racial composition.