Alternative approaches have led to different interpretations of the metropolitanization process in the United States. We identify and illustrate several methods and procedures for monitoring metropolitan-nonmetropolitan population change using the 1950-1980 U.S. decennial censuses. Two basic approaches are compared: constant area approaches and component methods. In addition, we assess the effects of changing metropolitan definitions on metropolitan-nonmetropolitan growth. The results clearly reveal that the underlying mechanics of metropolitanization not only are complex but have changed substantially during the 1950-1980 period. We conclude with observations regarding the use of these procedures in future research.