On spite of the fact that all theories of the origin of middle ear cholesteatoma are at least 75 years old, the immense knowledge on their biological behavior and composition and the information about their precursors and experimental induction of the defect in animals, their etiopathogenesis is still not clear. Moreover, in the last fifty years of great changes in therapeutic procedures treating tube-tympanic inflammations, substantial changes in the appearance of middle ear cholesteatomas emerged. The mesoepitympanic cholesteatomas after necrotic otitis disappeared, but mesotympanic forms of cholesteatomas were multiplied, including those below an uninterrupted ear drum, as well as the child-age cholesteatomas and those with well-developed pneumatization, where a congenital genesiswas in correctly suspected. The prevention is primarily based on preventing all types of tube-tympanic inflammations and myringitis, their complete healing up and, secondarily, in the therapy of precursors of cholesteatom, such as drainage and ventilation dysfunction of all aerial spaces of middle ear as well as certain kinds of ear drum dystrophy and, thirdly, in a perfect and timely operation on cholesteatoma.

        Key words: cholesteatoma, middle ear, prevention, cholesteatoma.