This study aims to investigate the determinants of service quality and the relationships of service quality, customer satisfaction, word of mouth and subsequent purchase intention of medical service. SERVQUAL, an instrument developed by the marketing area, is offered as a possible measure of medical service quality. SERVQUAL measures service dimension of tangibles, reliability, responsiveness, assurance and empathy. The questionnaire method is used in this study. A survey is conducted on patients who are randomly selected. The questionnaire are sent to 300 patients and 208 are available. The objectives of this study were: 1) to find out the influence of determinants of service quality on medical service. 2) to investigate the relationship of medical service quality and customer satisfaction. 3) to analyze the relationship of customer satisfaction and favorable word of mouth, ubsequent purchase intention 4) to find out the gap perceived service quality between secondary and tertiary hospital. The results of this study are summarized as follows: 1) Reliability, responsiveness and assurance have a positive impact on the medical service quality. 2) Medical service quality has a positive impact on the customer satisfaction. 3) Customer satisfaction has a positive impact on the favorable word of mouth and subsequent purchase intention. 4) There is no gap between secondary and tertiary hospital of perceived service quality.