This paper analyzes the performance of 38 Turkish natural gas distribution companies by using a non-parametric method, Data Envelopment Analysis (DEA). The results are used to determine the most proper model specification, to detect the important criteria affecting the efficiency levels, and to find the common characteristics of the most inefficient firms. We find that public firms compared to private firms, non-tender firms compared to tender firms, large firms compared to small firms and firms operating in more developed areas compared to firms operating in underdeveloped areas that utilize resources and manage costs more efficiently. However, we cannot reach a certain conclusion about the comparison of old firms versus the new firms. Lastly, we try to detect the common characteristics of the most inefficient firms and find that most of these firms are immature and low scale companies. Therefore, we think these firms can increase efficiency level either by increasing their delivery amounts through higher penetration rates or by merging or doing both together. (C) 2010 Elsevier Ltd. All rights reserved.