Mirror jitter is a flow-induced vibration phenomenon typical of convectively cooled optics. Flow separation points within the coolant supply lines, mirror manifolding, and mirror coolant passages produce internal turbulent pressure distributions, which lead to unbalanced fluctuating forces and resultant mirror jitter. The author reviews the known causes of jitter, methods to determine jitter forces as well as actual mirror jitter, and methods to measure jitter forces. A summary of known jitter force measurements is given, and an extensive bibliography of relevant literature is listed. Guidelines for evaluating system jitter and avoiding pitfalls are offered.