Drawing stimulus from parental acceptance–rejection theory (PARTheory), which postulates a pancultural association between perceptions of parental acceptance–rejection and offspring’s (children’s and adults’) psychological adjustment, this article describes the International Father Acceptance–Rejection Project along with the results of 13 studies in 11 nations. These studies not only test this postulate but also more importantly explore the question of whether offspring’s perceptions of parental power and parental prestige tend to moderate the relationship between perceived parental acceptance and offspring adjustment. This question derives from the fact that offspring’s perceptions of their fathers’ acceptance sometimes have a greater impact on the psychological adjustment of youth than do offspring’s perceptions of their mothers’ acceptance. Sometimes, however, offspring’s perceptions of their mothers’ acceptance have a greater impact on adjustment than do offspring’s perceptions of their fathers’ acceptance. And sometimes there is no significant difference in the impact of one parent’s acceptance versus the other parent’s. This much is known. But what is not known is, Why or under what conditions do the love-related behaviors of one parent have a greater impact on the adjustment than the love-related behaviors of the other parent? Results of research described in this Special Issue point in the direction of one class of conditions that helps to answer this question.