 The study found that only 22.5 percent of 235 rigorous evaluations of guideline dissemination and implementation studies published between 1966 and 1998 used theories, with precede being the most commonly used theory. The majority of studies used only one theory, and there was poor justification for the interventions until at least 1998. Future research should explicitly identify the justification for interventions, and use more explicit theory to advance implementation science.