It was shown in the preceeding letter that dimuon production by 22 GeV pions proceeds in part through qq̄ annihilations in agreement with the Drell-Yan model. Using these data we extract the quark distribution function of the pion. Comparison of our structure function with that obtained from data at higher energy reveals differences compatible with the QCD calculations of the Q 2-dependence (scale breaking) of the pion structure function.