This year marks the 25th anniversary of the year that the late Enrico Jones first published his manual for the Psychotherapy Process Q-set (PQS). The manual has since been published in Jones' landmark book, Therapeutic Action (2000), and was recently revised and updated by the Massachusetts General Hospital Psychotherapy Research Program. In this article, we mark the 25th anniversary of the PQS by reviewing both the early findings from the measure and more current research driven by those first findings.