Public participation and engagement in decision-making regarding science and technology (‘PP&E’) is an increasingly common practice. But what is known of whether PP&E achieves its goals? Surprisingly, little research evaluates PP&E. We put forth three reasons why PP&E advocates and practitioners should take evaluation seriously: the absence of evaluation causes PP&E’s advocacy to fail a minimal burden-of-proof standard; PP&E’s costs are greater than they appear; and these costs may be disproportionately borne by the already-disadvantaged. Evaluating PP&E would require identifying PP&E’s objectives and assessing its success in meeting them. To this end we survey scholarship advocating PP&E and identify three sets of objectives: substantively improving decision-making, deontologically fulfilling widely-held norms, and politically redistributing power away from techno-scientific elites. While there is some ad hoc evidence of progress toward these goals, we find no robust evaluation of PP&E. We offer four recommendations that might assist in evaluating PP&E more thoroughly.