The authors conducted a prospective study of fractional CO2 laser treatment of mature burn scars, comparing objective and subjective scar measurements evaluating at least one treatment and one control scar on the same patient pre- and post treatments. After institutional review board approval, burn survivors with mature blatant burn scars were invited to enter the study. A series of three fractional CO2 laser treatments was performed in an office setting, using topical anesthetic cream, at 40 to 90 mJ, 100 to 150 spots per cm2. Subjective and objective measurements of scar physiology and appearance were performed before and at least 1 month after the treatment series on both the treated and the control scar. A total of 80 scars, 48 treatment and 32 control scars, were included in the study. Treatment pain score averaged at 4.7/10 during and at 2.4/10 5 minutes after the treatment. All treated scars showed improvement. Objectively measured thickness, sensation, erythema, and pigmentation improved significantly in the treated scars (P = .001, .001, .004, and .001). Elasticity improved, but without statistical significance. Vancouver scar scale assessments by an independent observer improved from 8 to 6; patient self-reported pain and pruritus remained unchanged in both groups. Fractional CO2 laser treatment is a promising entity in the treatment of burn scars. Our study results show significant differences in objective measurements between the treated scars and the untreated control scars over the same time period. In scar treatment studies, the patient/observer and Vancouver scar scales may not be sensitive enough to detect outcome differences.