High-power, acoustooptic Q-switched red laser output is obtained by intracavity frequency-doubling a Nd:YAG laser operating at wavelength of 1.319 microm with a LiB(3)O(5) (LBO) crystal. 28 W average power at 659.5 nm was demonstrated at 5 kHz and a pulse width of 250+/-10 ns (FWHM). The beam quality of M2 value is 22+/-3 in both horizontal and vertical directions. The conversion efficiency and the stability of the red laser output power at 659.5 nm were both improved through the suppression of 1.338 mum operation by means of a thin YAG etalon. The long-term stability of the red light is better than 1% at an output of 23 W during 200 hours.