This paper demonstrates that a pollution tax with a …xed cost component may lead, by itself, to segregation between clean and dirty …rms without heterogeneous preferences or increasing returns. We construct a simple model with two locations and two industries (clean and dirty) where pollution is a by-product of dirty good manufacturing. Under proper assumptions, a completely strati…ed con…guration with all dirty …rms clustering in one city emerges as the only equilibrium outcome when there is a …xed cost component of the pollution tax. Moreover, a strati…ed Pareto optimum can never be supported by a competitive spatial equilibrium with a linear pollution tax. To support such a strati…ed Pareto optimum, however, an e¤ective but unconventional policy prescription is to redistribute the pollution tax revenue from the dirty to the clean city residents. JEL Classi…cation: D62, H23, R13.