Interactions of suburban cities with a central city as well as their proximity to the central city may have significant implications for their growth or decline. However, existing studies have focused on local factors to examine urban growth or decline without full considerations of interactions with their central cities. This paper aims to estimate the effects of the interactions between central city and suburban cities on the growth or decline of suburban cities using a simultaneous equations model for the five largest metropolitan regions. Three models for population, employment, and GRDP are specified with interaction variables, measured by travel O/D data between central cities and suburban cities, as exogenous variables. The results show that the interaction patterns and their effects are different between the capital region and other regions. For example, while the commuting from suburban cities to a central city is negative to population growth of suburban cities, positive in the capital region. The results imply that such interactions as well as local factors should be taken into account for developing urban regeneration policies for suburban cities at the regional level.