Pion Double Charge Exchange above the Δ(1232) Resonance

First measurements of exclusive cross sections for the (π+, π−) reaction at incident energies of 300–500 MeV are reported. For the analog-state transitions in 14C and 18O the 5° cross sections are found to remain nearly constant in this energy interval. This behavior is in disagreement both with predictions based on six-quark cluster models and with simple expectations based on recent single-charge-exchange measurements.