Although in knowledgeable hands treatment of vascular lesions is unlikely to result in permanent unwanted sequelae, complications do occur. Erythema and edema are common side effects and can be treated with supportive care. Pigmentary abnormalities and scarring are among the most feared risks. In addition, vesiculation, purpura, and infection are also potential side effects, and if severe may increase the possibility of untoward permanent consequences. Ocular damage is a rare but devastating complication of laser use. In all areas, attention to detail and prevention are the best means to avoid sequelae. This chapter aims to review these possible complications with pathophysiology and common treatment options for each area. © 2014 S. Karger AG, BaselLaser therapy in vascular lesions is based upon the laser's ability to supply a destructive dose of thermal energy to affected tissues. The capability to selectively target specific structures, termed 'selective photothermolysis', is possible based on adjustments in laser parameters of wavelength, pulse duration, fluence, irradiation, and spot size to match the therapeutic parameters required by the target tissue [1]. Unfortunately, this selectivity can be imperfect due to overlapping absorption spectra of targeted and untargeted tissues, as well as target tissue heat energy dissipation to surrounding untargeted tissues, resulting in collateral damage [1,2]. All lasers have some risk of complication, and the complication rate further varies based on the individual patient, lesions, and operator [3,4]. This chapter details complications that have been shown to arise with vascular laser surgery. The topics are organized by complication in order of frequency of occurrence, with pathophysiology and examples of complications, and recommendations for prevention and treatment should complications occur.