A theory is developed to model the behavior of mobile ions around a fixed charged distribution in the presence of dielectric bodies. By treating the short and long-wavelength fluctuations of the electric potential within different approximation schemes, this approach combines the strengths of the mean field approximation and the strong coupling expansion, while retaining the simplicity of the commonly used Poisson-Boltzmann theory. It is capable of accurately describing ion-correlation induced phenomena, such as the attraction between two like charged plates, the repulsion between two oppositely charged plates, and overcharging. The theory is compared with Monte Carlo simulation data for various systems of charged plates with their associated counterions and added electrolyte. Good agreement is found for nearly all conditions examined. © 2009 The Royal Society of Chemistry.