Traumatic panniculitis can be induced through the injection of various substances into the subcutaneous fat, especially in patients with psychiatric problems. This condition can also be caused through the subcutaneous implantation of different materials for cosmetic or therapeutic reasons or through mechanical or physical means. The diagnosis is always worth considering in those patients with bizarre clinical lesions and inflammatory changes in the subcutaneous fat that defy ready classification. There have been reported cases of traumatic panniculitis induced by acupuncture, but no reported cases associated with laser therapy. Fractional photothermolysis is the newest approach to laser therapy, with multiple micro-laser beams that target water-containing tissues to cause photocoagulation of narrow columns of skin. The penetration depth of the multiple micro-laser beams is up to 900μm, generally to the reticular dermis level. A 19-year-old female patient presented with a tender 4×7 cm sized erythematous to brownish, irregularly shaped, atrophic plaque on the right shin. She was treated for a leg scar using a 1,550 nm erbium fiber laser. Histopathologic examination showed moderate inflammatory infiltration and lipomembranous fat necrosis in the subcutaneous septa with mild inflammation in the overlying dermis. The tissue proved to be infiltrated by lymphohistiocytic cells and a few eosinophils. The patient was treated with systemic and topical corticosteroids; she has experienced no recurrence. We report an interesting case of traumatic panniculitis following fractional laser therapy. (Korean J Dermatol 2009;47(3):354∼357)