Results describing the response of resonant tunneling devices to an applied high-frequency harmonic bias are produced. Appropriate coefficients for rectification, linear admittance, and generation of higher harmonics are calculated. We have shown that rectification preserves the low-frequency values up to frequencies of about 1014 Hz. At the same time linear admittance and higher harmonic generation coefficients decrease sharply at frequencies higher than the energy width of resonant level. At high frequencies reactive components of the tunneling current appear to dominate.