The objective was to assess the efficacy of red light phototherapy with a portable device in acne vulgaris.  Twenty-eight volunteers with mild to moderate acne were treated with portable red light-emitting devices in this split-face randomized trial. The right or left side of the face was randomized to treatment side and phototherapy was performed for 15 minutes twice a day for 8 weeks. Clinical photographs, lesion counts, and a visual analog scale (VAS) were used to assess each side of the face at baseline and Weeks 1, 2, 4, and 8, and a split-face comparison was performed.  The percent improvement in noninflammatory and inflammatory lesion counts of the treated side was significant compared to the control side (p<.005). VAS decreased from 3.9 to 1.9 on the treatment side and the difference between the treatment and control sides was significant at Week 8 (p<.005).  This study shows that red light phototherapy alone can be a new therapeutic option for acne vulgaris.