Services Quality is an area of opportunity for IT service providers to innovate and deliver outstanding results to their customers. The objective is to minimize the variance of key quality indicators and deliver predictable capabilities. In this paper we adopt the Lean Sigma methodology from the manufacturing domain as a quality control framework and propose an optimized system model for managing predictability and reducing cost in the IT incident management process. The model establishes guidelines for receiving, classifying and distributing work in a service delivery organization. It defines metrics, controls and management objectives. Using simulation, we conduct an extensive numerical study to show how the model behaves under different operational scenarios that reflect a diverse skill base, the presence of service level objectives, and incoming work with varying levels of complexity. In addition, we provide managerial insight into what drives performance and illustrate the trade-offs between different service delivery designs. © 2010 IEEE.