On the basis of fairness heuristic theory, the authors provide an explanation of the frequently replicated fair process effect (the finding that perceived procedural fairness positively affects how people react to outcomes). The authors argue that, in many situations, people may find it difficult to assess whether their outcome is fair or unfair and satisfying or unsatisfying because they only have information about their own outcome and they do not know the outcomes of others and that, in these situations, people use the fairness of the procedure as a heuristic substitute to assess how to judge their outcome. The results of 2 experiments corroborate the authors' line of reasoning. Findings are discussed in terms of recent developments toward an integration of the procedural and distributive justice domains.