An important characteristic of the U.S. population is its geographic mobility. In 1970, 18 percent of the population was living in a county that was different from their 1965 county of residence; half of these migrants had also moved across state lines. Previous work on geographic mobility can be classified into two categories. The first is composed of studies that have used aggregate data (for example, Samuel Bowles, Michael Greenwood, 1969, Ira Lowry, and Aba Schwartz) to examine the determinants of net or gross migration for SMSAs or other geographic divisions. The second category of research has used data on individuals (for example, Julie DaVanzo, Richard Kaluzny, John Lansing and Eva Mueller, and Solomon Polachek and Francis Horvath) to explore the relationship between an individual's characteristics and his decision to migrate. This article continues the work on the analysis of the individual's decision to migrate, but differs from the previous studies by focusing on the relationship between job mobility and migration. First, the proportion of geographic mobility that occurs in conjunction with a job change is calculated. Second, it is shown that the true effects of human capital variables, job characteristics, and family variables on the decision to migrate are best measured when one takes account of the relationship between migration and job mobility. Third, the effect of migration on the wage gains of individuals is studied and again the need for distinguishing among moves that were associated with quits, layoffs, and transfers is clearly shown. Finally, by using three data sets that encompass different age groups (the National Longitudinal Surveys (NLS) of Young and Mature Men and the Coleman-Rossi Retrospective Life History Study), the importance of the relationship between migration and job mobility is demonstrated at different points in the life cycle. Section I of the article presents some summary statistics on the extent of geographic mobility among the individuals in the samples and documents the relationship between migration and job mobility. In Section II a framework for analyzing the decision to migrate is discussed. Sections III and IV present the empirical results while Section V summarizes the analysis. (excerpt) - See more at: http://www.popline.org/node/454676#sthash.CWLPkaek.dpuf