The resonance-enhanced multiphoton ionization (REMPI) spectrum of NO has been obtained in the range of 420 - 480 nm with a Nd:YAG pumped optical parametric generator and amplifier. The spectral lines can be attributed to NO X^(2)(v" = 0; 1) → A^(2)Σ(v' = 0; 1) transitions. In this wavelength range, NO molecules are ionized via the resonant intermediate state A^(2)Σ^(+) and by a (2 + 2) REMPI process. The dependence of ion signals on laser intensity and gas pressure is discussed. The variation of the ionization signal versus laser intensity is near quartic. This is in good agreement with theory.