Background: Postinflammatory hyperpigmentation (PIH) is the most common skin complication in Asians after invasive cosmetic treatments., Objective: To determine whether oral tranexamic acid (TA) reduces the incidence of PIH after Q-switched ruby laser (QSRL) treatment., Methods and Materials: Thirty-two Japanese women underwent QSRL treatment for senile lentigines on the face. They were randomly divided into two groups that did (n=15) and did not (n=17) receive oral TA treatment (750 mg/d) for the first 4 weeks after QSRL treatment. Nineteen participants had melasma-like maculae at baseline. Clinical and colorimetric assessments were performed at baseline and 2 and 4 weeks later., Results: Pigmentation was effectively treated using QSRL at 2 weeks, but PIH was frequently seen at 4 weeks. There was no significant difference in the incidence of PIH between participants who received oral TA and those who did not. The presence of melasma did not influence the effectiveness of the treatment., Conclusion: Although oral TA has been reported to have depigmentation effects, it may not be effective for preventing PIH after QSRL. Considering the dosage and duration of treatment, an optimal protocol may be needed to induce the efficacy of this treatment to achieve the PIH-preventing effect of oral TA., (© 2011 by the American Society for Dermatologic Surgery, Inc.)