Abstract The new high- T c oxide superconductors have an unusually large energy gap (Δ) to Fermi energy ( E F) ratio compared to conventional superconductors. This ratio could even be greater than unity. Our calculations estimated the relative stopping power change due to the transition to the superconducting state as a function of energy gap and the energy of a proton. The stopping power change is large for low-energy projectiles. Experimental efforts to measure relative stopping powers to an 0.14% accuracy are also discussed.