A surgical instrument for uterocervical diathermic conization has been constructed for adequate treatment of patients with mild to severe dysplasia (CIN I-III) of the uterine cervix. The purpose of the instrument is to provide a simple means of performing a differentiated conization tailored to the anatomy of the patient and the extent of the disease. With this instrument conization of the uterine cervix may be performed on an out-patient basis. It includes a mount holder member for a diathermic wire that fits into a pistol grip. The wire is held in tension by the mount so that the wire forms an angle a to the longitudinal axis of the mount. The wire then cuts out a cone when the mount is turned through a complete revolution. Angle α of the wire may be adjusted on the mount thus enabling variation in the size and shape of the cone that is excised.