The Q-switched alexandrite laser used at 752 nm, a wavelength well absorbed by melanin relative to other optically absorbing structures in skin, causes highly selective destruction of pigment-laden cells. In addition, the 75-nanosecond pulse duration produced by this laser approximates the thermal relaxation time for melanosomes, thereby confining the energy to the target. Facial and labial dark brown macules quickly identify patients with Peutz-Jeghers syndrome. These lentigines may be cosmetically disfiguring. The Q-switched alexandrite laser produces clinically significant fading of mucocutaneous melanosis in association with Peutz-Jeghers syndrome without complications often seen with other therapeutic modalities.