This prospective, randomized study compares, for the first time, measured blood loss at conization and within 24 hours after using either the cold knife technique or the carbon dioxide laser scalpel. One hundred and ten consecutive patients were evaluated. The median blood loss in the laser group of 55 patients was 4.6 milliliters at, and within, 24 hours after operation compared with 30.1 milliliters in the cold knife group of 55 patients. More important, however, is that the corresponding figures for the range of bleeding were 0.4 to 155.4 milliliters and 5.6 to 1,570.9 milliliters, respectively. The incidence rate for bleeding complications requiring surgical intervention was 1.8 per cet for the laser group and 14.6 per cent for the cold knife group. This difference was statistically significant, p less than 0.015--Fischer's exact test. Conization for treatment of premalignant changes of the cervix uteri will probably remain the treatment of choice for some time to come. It is our opinion that, in the future, laser conization will replace cold knife conization.