The study undertakes a literature review to establish systematic typologies of customer variability and employee variability in the service industries. A conceptual model of the incidences of these various types of variability in the service provision process is then presented. Using the typology and the model, a quantitative survey of managers from leading Taiwanese service firms is then undertaken to ascertain the prevalence and significance of the different types of variability in a range of service industries. In general, customer variability is found to be more prevalent than employee variability across all the service industries studied here. Significant differences are also detected among the individual service industries. The study provides valuable empirical evidence regarding the types of variability that require attention in particular industries if superior service quality is to be achieved. Few have undertaken such a systematic typology of variability and its applications in service industries