摘要： Melasma represents the most obvious and disfiguring change of the face leading to psychological problems especially in females. Ablative lasers have also been used by many professionals to treat melasma, although there is few scientific data supporting this indication. The exact mechanism of action of ablative lasers in melasma is not yet clear enough. We aimed to evaluate the ultra- structural effect of fractional ablative CO2 (FrCo2) laser on facial melasma. Eleven melasma patients evaluated clinically by clinical modified area and severity index (MASI) score, treated by two sessions of fractional CO2 laser one month a part. Two punch biopsies of 2 mm diameter were obtained from all subjects one before and the other 3 months after treatment. All biopsies were analyzed by light and electron microscopy. Clinically, significant improvement of pigmentation and 48% reduction of (MASI) score were observed after two sessions of laser treatments. Light microscopic analysis of specimens revealed significant decrease in melanocyte count after treatment. Electron microscopic analysis of specimens after treatment revealed significant decrease in the number and size of melanocytes and significant decrease or complete absence of melanin granules in the surrounding keratinocytes compared to pre-treatment specimens. No scarring or post inflammatory hyper or hypopigmentation. We concluded that repeated application of Fractional CO2 laser on melasma skin may result in long lasting improvement due to its destructive effect on melanocytes.