This text, intended for a first course in performance evaluation, provides a self- contained treatment of all aspects of queueing theory. It starts by introducing readers to the terminology and usefulness of queueing theory and continues by considering Markovian queues in equilibrium, Little’s Law, reversibility, transient analysis and computation, and the M/G/1 queueing systems. Subsequent chapters treat the theory of networks of queues and computational algorithms for networks of queues. Stochastic Petri networks, including those whose solutions can be given in product form, are covered in detail. A chapter on discrete-time queueing systems, which are of recent interest, discusses arrival processes, Geom/Geom/m queueing models, and case studies of discrete-time queueing networks arising in industrial applications.