This paper derives a gravity equation for commuting and uses it to identify the effect of regional borders on commuting. We build on the seminal trade paper by Anderson and Van Wincoop (2003) and highlight some interesting similarities between our model and Wilson’s doubly constrained gravity equation (Wilson, 2010), a workhorse model from spatial interaction theory. The model is estimated by applying a negative binomial regression method on Belgian intermunicipal commuting data. We show that regional borders exert a sizeable residual deterrent effect on commuting, a finding with obvious implications for regional labour market integration. This border effect differs significantly between regions and depends on the direction in which the border is crossed. ; JRC.J.2 - Knowledge for Growth