In cryosurgery, a rapid double freeze using liquid nitrogen spray coupled with a slow thaw generates optimum cell destruction. Important factors in using the cryosurgical technique include temperature monitoring of the lesion, the type of instrumentation, the type of cryogen, and the nonhomogeneity of human tissue. Physiological processes occurring subsequent to cryogen application cause tissue necrosis. Cryosurgery is indicated for treatment of some basal cell carcinomas and occasional squamous cell carcinomas; most other lesions should be treated by surgical excision at the present time. The authors are involved in research to determine means of observing tissue destruction, temperature monitoring and control methods, and evaluation of post-thawing processes.