Costa and Kahn hypothesize that the growing concentration of skilled couples in large cities is due to their migration to large cities to solve their dual-employment problem. However, there is only limited empirical evidence in support of this hypothesis. This research tests an alternative hypothesis: The intermetropolitan distribution of skilled couples is largely the result of marriages among skilled singles in large cities. The relative merits of both the “co-location” and “marriage market” hypotheses are evaluated by comparing the effects of migration and marriage on the intermetropolitan distribution of dual-degree couples using data from the 2008 American Community Survey. Migration is found to have little effect on the distribution of dual-degree couples. Rather, the concentration of dual-degree couples is strongly related to the high rate of marriages among single college graduates in the same cities.