The migration efficiency ratio of an area is defined as the net migration of the area (in-migrants minus out-migrants) divided by the total number of moves whose origin or destination is that area (in-migrants plus out-migrants) multiplied by 100. This paper investigates variations in migration efficiency from 1955 to 1960 among Standard Metropolitan Statistical Areas with populations of 250,000 or more. Regional variation in migration efficiency was evident, ranging from an average of −9.7 in the Northeast to 19.6 for SMSA’s in the Western region. Nonwhites tended to have higher migration efficiency than whites. Rapidly growing metropolitan areas had higher migration efficiency ratios than areas growing at a lower rate or losing population. The educational level of a metropolitan area, as measured by the percent of the population 25 years old or over with at least a high school education, was positively related to migration efficiency. The composition of the migrant population, both in- and outmigrants for a given area, was related to the value of the migration efficiency ratio. If the migrant population contained a large proportion of persons aged 20–34, migration efficiency was low, regardless of the direction of the major migration stream. Region was found to have a major effect. Variables that had a strong and positive relationship with migration efficiency in one region were usually found to have no relation, or a negative relation, with it in other areas. Obviously, further research is needed for the identification of factors producing these strong regional effects.