Randomized clinical trials support the efficacy of a wide range of psychoeducational interventions. However, the mechanisms through which these interventions improve outcomes are not always clear. At times, the theoretically specified factors within interventions have been shown to have specific effects on patient outcomes. But it has also been argued that other factors not identified in the intervention theory (e.g., "nonspecific" factors such as patient expectations and therapeutic patient-clinician alliances) have powerful nonspecific effects that account for most, if not all, of the observed efficacy of psychoeducational interventions. This article describes important concepts in this debate and discusses key issues in distinguishing between specific and nonspecific effects of psychoeducational nursing interventions. Four examples are used to illustrate potential methods of identifying and controlling for nonspecific effects in clinical intervention trials.