Cryosurgery is a controlled refrigeration technique used to destroy some tumoral tissues that are more sensitive to congelation than healthy tissues. The authors present its principle and describe the apparatus: a source of liquid nitrogen, a flexible tube and a probe with a skin-suitable nozzle. The main advantages of the method are its reliability and reproductibility. Among the numerous indications of cryosurgery are all benign tumours of the skin, especially when they are multiple. Concerning malignant lesions, the most usually treated are the multiple forms of basal cell carcinoma, notably the superficial type. Although cryosurgery acts blindly, its indications are increasingly better defined.