The Dutch Catholic Church has experienced an immense growth and an equal measure of decline in the last two centuries. Four phases can be discerned: slow growth 1795-1870; fast growth 1870-1960; early decline 1920-1960; decline 1960-. Existing explanations for these developments seem not fully adequate: they either explain growth or decline (never both) or explain the development of the Church by its social organizations. An alternative is offered by the sect-to-church theory, as has been developed by the rational choice theory of religion. This theory explains the growth and decline of a church by the degree of tension it has with society and the stakes in conformity it offers. Historical evidence shows that in times of growth, the Dutch Catholic Church offered valuable stakes in conformity and was in high tension with society; conversely, that in times of decline the church offered less valuable stakes in conformity and reduced its tension with society. An extra chapter explains why despite new (sectarian) policy after 1970, the commitment has not increased: this policy was never fully realized and faced severe resistance from the ground levels. Rational choice theory is a useful theory to explain the development of Dutch Catholicism and it is advised to test this theory more elaborate on European religion. However, the Catholic Church doesn't fit automatically in the theory that seems to start from small, protestant, and American sects. In the epilogue, some practical consequences of rational choice theory for church life are elaborated.