Whether lax environmental regulations are an important attraction for mobile capital remains one of the most controversial issues in the area of regulatory federalism. While the extant literature does a nice job of estimating the effects of environmental regulation on the spatial allocation of new plant births, one neglected area of research is the effect that environmental regulation has on plant relocation decisions. This paper uses an annual (1980-90) county level panel data set to examine the relationship between air quality regulatory stringency and the destination choice of relocating plants. We estimate empirical models using both parametric and semi-nonparametric specifications. Empirical results from both models suggest that air quality regulations alter significantly the destination choices of relocating plants.