The autosomal dominant hereditary Treacher Collins syndrome manifests itself phenotypically in dysmorphogenesis of particularly the first, but also the second branchial arch system. Consequently, 50% of patients with Treacher Collins syndrome have a congenital, generally pure conductive hearing loss resulting from a major or minor ear anomaly. The outcome of surgery to improve patients' hearing varies and is sometimes even disappointing. Thorough analysis of 33 cases (39 operated ears) and the strict application of a classification for the anomaly to each ear enabled us to gain insight into the most suitable surgical policy and to form a prognosis for reconstructive ear surgery.