In empirical psychotherapy research the randomized controlled trial (RCT) is considered the gold standard. Its fundamental rationale is that studying the efficacy of a given treatment method requires a way to systematically compare the effect of this method with the effect of another—preferably approved—treatment. RCTs are characterized by certain fundamental problems, which require us to be cautious to draw very far-reaching practical implications of RCT findings, for example concluding that patients with a certain diagnosis should always be offered a certain specific treatment.