This document discusses key performance measures for call centers and contact centers. It identifies 18 performance measures across categories of service, quality, efficiency, and profitability. These measures become more complex as call centers evolve into multi-dimensional outsourcing providers offering various support services. Performance must be analyzed considering both ordinary call center work as well as more advanced multi-level support. Key measures include block rates, abandonment rates, self-service usage, first resolution rates, agent occupancy, conversion rates, and cost per call.