The aim of this work is to study gray tracking during type II second-harmonic-generation 1064→532 nm in halide flux grownKTiOPO4crystals. The repetition rate of the laser varies from 1 to 20 kHz. We experimentally demonstrate that the gray-tracking threshold, expressed by the harmonic peak power density, is a decreasing exponential function of theQ-switch frequency. The corresponding 532 nm average power density, however, remains constant. ©1997 American Institute of Physics.