A direct relationship exists between the power density of a carbon dioxide laser and the thickness of scars it produces in rat skin. Statistically significant positive relationships were noted between laser power and scar thickness at days 14, 21, and 32. The slope of the curve increased as the number of days elapsed. At day 32, the ratio of scar thickness to CO2 laser power density delivered was 0.3 microns/W-cm2. Scar formation took longer for completion at higher wattages of irradiation.