The design of an ac superconducting solenoid capable of producing oscillatory magnetic fields having peak‐to‐peak amplitudes as large as 1000 G at frequencies up to 500 Hz with only moderate dissipation is discussed. It is shown that a simple, inefficient coil geometry (thin solenoid) is suitable. Tests with an ac superconducting solenoid used as a modulation coil in a 60 kG superconducting magnet are described. Results indicate that the performance of copper at 4.2°K is far surpassed by Nb‐25% Zr over a wide range of operating conditions.