After several decades of population deconcentration in American metropolitan areas, examination of 1970 to 1975 data suggests tentatively that deconcentration has not recently slackened. Population deconcentration or suburbanization has not reversed, and there is no evidence of faster growth in central cities than in suburban areas. This study uses demographic data on over 200 Standard Metropolitan Statistical Areas (smsas) in 1970 and 1975, comparable to the fewer number ofsmsasin 1950 and 1960, for a study of 25 years of change in metropolitan population distribution. Two-point estimation of the negative exponential function provides a useful, efficient summary of urban population densities for eachsmsain 1950,1960,1970, and 1975. Using these data, descriptive and multivariate statistics show the association of population concentration, measured by central densities and density gradients, withsmsapopulation size, central city age, region, and time period.