Numerous studies have examined the relationships between religious fac
tors and aggregate suicide rates, with inconsistent findings. We exten
d research on this topic by focusing on an overlooked variable: religi
ous homogeneity, or the extent to which community residents adhere to
a single religion or a small number of faiths. After developing a seri
es of arguments linking religious homogeneity with lower suicide rates
, we investigate this relationship using 1980 data on 296 SMSAs. As hy
pothesized, religious homogeneity is inversely associated with suicide
rates; its estimated effects are greater than those of the other reli
gious variables that am widely used in studies of suicide - percent Ca
tholic and church member rates - and they persist despite controls for
established covariates of suicide rates. On closer inspection we find
regional differences in the apparent influence of religious homogenei
ty. Protective effects are strongest in the SMSAs of the Northeast, an
d they also surface in the South, while they am weaker in other areas
of the U.S.