This study sought to identify the degree of social mobility across generations and to develop causal models of the sponsors of this mobility. The sample for the study consisted of 7,835 young adult males from the Fourth Follow-Up survey of the National Longitudinal Study. The study analyzed the relationship between mobility and such antecedents as subjects' years of education, fathers' years of education, and class rank. It also analyzed the impact of fathers holding low-status or high-status jobs. An index of mobility was developed by computing the difference between the status rankings of fathers and sons. Analyses indicated considerable mobility in the sample. It is concluded that upward mobility is indeed present in modern American society. However, while there is mobility, sons in the lower reaches will not rise too far and sons in the upper reaches will not fall too far. (JDD)