ABSTRACTIn recent years, service quality has developed into one of the most considered success drivers because of its relevance to service providers' economic success. Furthermore, it is acknowledged in theory and management practice, that internal service processes are the prerequisite of high external service quality. This paper explores internal service processes by enlarging Parasuraman, Zeithaml, and Berry's GAP model (1985; 1988). By analysing internal information asymmetries in the delivery of service quality, hypotheses about internal drivers of external service quality are formulated and tested by empirical data from Swiss bank employees. The results are the basis for a quality-oriented Internal Marketing in service organizations.