The central objective of Men in a Developing Society is to show, as concretely as possible, how men experience a period of rapid economic development, particularly in the areas of migration, occupational mobility, and status attainment. It is based mainly on a sample of 1,640 men in Monterrey, Mexico, a large and rapidly growing manufacturing metropolis in northern Mexico with much in-migration, and a sample of 380 men in Cedral, San Luis Potosi, a small, economically depressed community with high rates of out-migration, much of it to Monterrey. The study of men in Monterrey is perhaps the most thorough one yet conducted of geographic and social mobility in a Latin American city. In part, this was possible because of the innovation of collecting complete life histories that record what each man was doing for any given year in the lay areas of residence, education, family formation, and work. These data permit the effective use of the concepts of life cycle and cohort analysis in the interpretation of the men's geographic and occupational mobility. The experience of the Monterrey men in adapting to the varied changes required by their mobility was not found to be as difficult as is often indicated in the social science literature on the consequences of economic development. In part this may be because Monterrey, in comparison with most other Latin American cities, has been unusually successful in its economic growth. The impact of migration also was lessened because most of the men had visited the city prior to moving there and many had friends or relatives in the city. The age of the migrants upon arrival in Monterrey made a significant difference in subsequent occupational mobility; those of nonfarm background who arrived before age 25 fared better than natives of the city. Although it appears that status inheritance in Monterrey is somewhat higher than in industrialized countries, a considerable proportion of men do move up the occupational ladder. And perhaps as important, the Monterrey men, whether or not they themselves are moving up, perceive the society as an open one. The very success of Monterrey's development created conditions that would bring about changes in the educational, economic, and cultural expectations of its inhabitants. Thus, paradoxically, the general satisfaction and the lack of group and class conflict in Monterrey over the previous decades may well have given rise to future dissatisfaction and conflict.