This study examines, for the case of Catholics, the thesis that a “critical mass” of devoted faculty members—50 percent or more, according to the papal document Ex Corde Ecclesia—serves to promote or preserve the religious character of religiously affiliated institutions of higher education. Factor analysis and structural equations are employed to analyze a random sample of faculty members ( n= 1,290) and institutional profiles ( n= 100) of American Catholic colleges and universities. Catholic faculty show higher support for Catholic identity in latent structures of aspiration for improved Catholic distinctiveness, a desire for more theology or philosophy courses, and longer institutional tenure. Institutions having a majority of Catholic faculty exhibit four properties consistent with stronger Catholic identity: a policy of preferential hiring for Catholics (“hiring for mission”), a higher proportion of Catholic students, higher faculty aspiration for Catholic identity, and longer faculty tenure in the institution. These latter two characteristics are not due simply to aggregation, but are stronger, on average, for Catholic faculty when they are in the majority. Preferential hiring marks Catholic identity, but is ineffective to increase the proportion of Catholic faculty. I conclude that the prediction of the critical mass thesis is correct.