and loyalty; a test of mediation. He studied a quality of service, customer satisfaction & loyalty: a test of mediation. This research was conducted with a bank in Tehran, Iran, in 2009 and 2010 that aimed to determine the quality of services offered by Sepah Bank, and studied of the relationship between service quality, customer satisfaction and loyalty. The research illustrates that in every five dimensions of service quality (reliability, responsiveness, assurance, empathy tangibility.) in fact, research has shown that, although all five dimensions of performance in all of the Sepah Bank has received higher-than-average credit limit, which in both cases of assurance and tangibles have the most and the least relation with the customer satisfaction and loyalty. But it did not meet the expectations of the customer.