LETTER TO THE EDITOR: Exact critical exponent for the shortest-path scaling function in percolation

It is shown that the critical exponent g₁ related to pair-connectiveness and shortest-path (or chemical distance) scaling, recently studied by Porto et al, Dokholyan et al and Grassberger, can be found exactly in two dimensions by using a crossing-probability result of Cardy, with the outcome g₁ = 25/24. This prediction is consistent with existing simulation results.