The CO2 laser has become a valuable tool for the treatment of lower genital tract neoplasia. The records of 52 women who underwent CO2 laser cervical conization were analyzed retrospectively to evaluate the effect of tissue thermal damage on histopathologic interpretation. Lesion evaluability, defined by the ability to diagnose neoplasia accurately in the specimen, was satisfactory in only 26 cases; in the other 26, thermal damage was severe enough to preclude accurate diagnosis. A postoperative diagnosis of cervical intraepithelial neoplasia III was made in 17 instances, and microinvasion was suspected but unverifiable in two of these. Two patients had frankly invasive cancer, but vascular space involvement in one could not be evaluated accurately because of thermal damage. Tissue thermal damage sufficient to interfere with accurate histologic evaluation was noted in the majority of laser conization specimens. The value of a conization is both diagnostic and therapeutic. The potential impact of a diagnosis compromised by thermal damage is serious.