The aim of the preoperative investigations of patients with hearing loss, including clinical, X-ray and audiometric examination, is to answer the following questions: How great a handicap does the patient have from his hearing loss? Is there any active infection, irritation or cholesteatoma present, which can defeat an operation to improve hearing? How well are the Eustachian tubes functioning? Are there any morphological or functional defects in the eardrum or ossicles? How well are the oval and round windows functioning? How good is the sensori-neural function? Not until these questions are answered is it possible to judge whether there are any indications for operation and what type of operation should be performed.