Ultraviolet A(1)(UVA(1)) phototherapy (spectral range 340-400 nm) is a well-established treatment option for various skin diseases such as localized scleroderma. Recent improvements of conventional UVA(1)light sources (metal-halide or fluorescent lamps) have brought attention to a new light-emitting diode (LED) technology with remarkable advantages in handling and clinical routine. This study provides a preclinical histological and molecular evaluation of an LED-based UVA(1)prototype with a narrower spectral range (360-400 nm) for treating localized scleroderma. Scleroderma mouse models and fibroblasts in vitro were exposed to LED-based UVA(1)phototherapy or to irradiation with a commercially available metal-halide lamp emitting low-dose (20, 40 J/cm(2)), medium-dose (60 J/cm(2)) and high-dose (80, 100 J/cm(2)) UVA(1)light. Both UVA(1)light sources affected inflammatory genes (IL-1 alpha and IL-6) and growth factors (TGFss-1 and TGFss-2). Increased collagen type 1 was reduced after UVA(1)phototherapy. Matrix metalloproteinase-1 was more enhanced after a medium dose of LED-based UVA(1)phototherapy than after conventional treatment. In vivo, dermal thickness and the amount of collagen were reduced after both treatment methods. Remarkably, myofibroblasts were more effectively reduced by a medium dose of LED-based UVA(1)phototherapy. The study indicates that LED-based UVA(1)phototherapy yields similar or even better results than conventional treatment. In terms of biosafety and patient comfort, LED-based UVA(1)phototherapy offers clear advantages over conventional treatment because of the use of a narrower and less harmful UVA(1)spectrum, less heat generation and shorter treatment times at the same irradiation intensity. Clinical studies are required to confirm these results in patients with localized scleroderma.