The authors are absolutely meticulous and unsparing in cataloging the formidable difficulties and limitations of outcome research. "Research into psychotherapy necessarily and inevitably changes the nature of the therapy it investigates," they say (p. 13), a sort of Heisenberg Principle run rampant. They address further complicating issues, such as comorbidity, the general versus the specific impact of a modality, and the built-in bias of certain scoring instruments to influence, or even dominate, the apparent outcome (for example, the Beck Depression Inventory tilts toward cognitive therapies, and the Hamilton Depression Rating Scale may favor medication outcomes). In addition, the tortuous natural history of many psychiatric disorders means the timing of follow-up may all but determine a study's efficacy findings. The editorial decisions, to systematize by diagnostic group rather than by treatment modality, and to omit most open trials, introduce consequences of their own. The authors make abundantly clear that the lot of the follow-up researcher is certainly not an easy one.