Differential cross section measurements were made for C13(γ, π+)B13(g.s.) at 90° (lab) for pion energies of 18, 29, and 42 MeV, and for C13(γ, π+)B13 (Ex=3.5 MeV) at 42 MeV. The ground-state results are compared to several distorted-wave impulse approximation calculations and to Helm model calculations. There are significant discrepancies between experiment and theory and among the theoretical results. NUCLEAR REACTIONS C13(γ,π+)B13 (Ex=0, 3.5 MeV), θπ=90° (lab), Eπ=18, 29, 42 MeV, measured dσdΩ, compared with DWIA calculations.