Objective. Both classical urban theory and the subcultural theory of u
rbanism predict that city-dwellers are relatively unconventional in th
eir behavior, and accumulated evidence is consistent with that predict
ion. However, it remains uncertain whether urbanism-the population siz
e of a community-actually promotes unconventionality. The purpose of t
his study is to assess urbanism's independent impact on unconventional
sexual activity. Methods. Data from the NORC General Social Survey ar
e analyzed, focusing on indicators of premarital sexual activity and c
ohabitation, marital infidelity, and homosexuality. The analysis compa
res these behaviors among residents of more urban and less urban commu
nities while controlling for personal characteristics and migration hi
story. Results. Findings show that urbanism promotes open homosexualit
y but not premarital sex, cohabitation, or marital infidelity. Paradox
ically, results also indicate that urbanism promotes permissive attitu
des toward most of these behaviors. Conclusions. That urbanism promote
s sexually permissive attitudes without necessarily promoting parallel
behavior is consistent with classical urban theory's view that urban
unconventionality is actually normful behavior within those subculture
s that depend upon urban population concentration for their viability.