This paper examines the association between fertility and religious affiliation among Puerto Ricans. Bongaarts' proximate determinants framework is used to compare religious categories on behaviors that directly affect fertility. We found no difference in recent fertility between Catholics and non-Catholics in Puerto Rico (total fertility rate = 2.5). We also found Catholics and non-Catholics to be similar on age at first marriage (23.3 and 23.4 years, respectively), contraceptive use (71 percent and 69 percent of married women currently contracepting), and breast-feeding practices (mean duration of breast-feeding of 4.4 and 4.3 months). Differences were observed between less committed and more committed Catholics in total fertility rate, age at first marriage, and contraceptive use, but these differences were not large and were in the opposite direction from the expected. Our findings support the theory of convergence of Catholic and non-Catholic fertility for the US. Our discrepancy with findings from the National Survey of Family Growth is evidence of the cultural diversity in the US Hispanic population and indicates the importance of disaggregating by ethnicity or national origin when studying this population.