Background: Pulsed dye laser treatment and other cosmetic procedures result in significant bruising. Claims have been made regarding the efficacy of topical vitamin K in both preventing and speeding the clearing of bruising; however, well-controlled studies are lacking. Objective: The purpose of this study is to evaluate the effects of topical vitamin K versus placebo in the prevention and clearing of laser-induced purpura. Methods: A total of 22 patients were enrolled in this double-blind randomized placebo-controlled study. The patients were divided into pretreatment and posttreatment groups; the 11 patients in the former group applied vitamin K cream to half of their face and vehicle alone to the other half of their face twice daily for 2 weeks before laser treatment. The latter group followed the same procedure for 2 weeks after laser treatment. On day 0, all subjects underwent laser treatment for facial telangiectases using a 585-nm pulsed dye laser. Bruising was rated by the both the patient and physician by means of a visual analogue scale on days 0, 3, 7, 10, 14, and 17. Results: The side of the face treated with topical vitamin K before laser therapy showed no significant difference in bruising as compared to placebo. However, the side of the face treated with vitamin K cream after laser treatment had significantly lower scores of bruising severity when compared with the side treated with placebo. Conclusion: Although pretreatment with vitamin K did not prevent bruising after laser treatment, use of vitamin K cream after laser treatment did reduce the severity of bruising, particularly in the initial days of application. (J Am Acad Dermatol 2002;47:241-4.)