Fifty years have passed since the post-World War II development of demography as an academic field. During this time, one of the central focuses of research has been the study of demographic and fertility transitions. The authors review a selection of research developments and analytic issues that have appeared in the literature. After presenting, in roughly chronological order, the general development of this research work, they raise questions concerning theory and methodology. In doing so, they argue that some research directions have been overemphasized to the neglect of others.