The Korean mobile telecommunication service market is faced with a tremendous competitive period, in which the market is entering into the maturity stage with launching of the 3rd generation service and with introduction of mobile number portability. In general, it is more important to sustain the old customers than to attracting new customers, as the life cycle of an industry is entering the maturity stage in which the growth rate of new customers is decreasing gradually or becoming stagnant. Until now, many researches had tested whether the customer satisfaction and loyalty were the core factors of sustaining customers or not. Also service quality and switching cost were given a remarkable attention for their possibility of exogenous factors, which could exercise effects to customer satisfaction and loyalty. In the same context, mobile telecommunication business has to seek a way to maintain the existing customers instead of promoting new customers. So this study investigates whether the service quality and switching barrier of mobile telecommunication could have effects on the customer satisfaction and loyalty, which are recognized as an efficient means to sustain the current customers. In order to test the hypothesis on the effects of service quality and switching barrier of mobile telecommunication to customer satisfaction and loyalty in Korean telecommunication industry, this study collected the questionnaire response data of students including middle and high school students and undergraduates, who are regarded as the major customers in that mobile telecommunication industry.