This chapter presents a survey of the statistical distributions applied to model X-band maritime surveillance radar clutter returns. Included is also a discussion, from a historical perspective, of the evolution of such models, which has coincided with improvements in radar resolution. In the early development of radar systems and their associated detection architecture, observed clutter returns were modelled adequately, in complex domain, by Gaussian processes. The non-Gaussian nature of maritime surveillance clutter was first reported in, and then confirmed by. In the latter, analysis of radar clutter from two separate trials were used to demonstrate the non-Gaussian property of sea clutter. In both trials, an X-band airborne radar was deployed by United States' Naval Research Laboratory (NRL), surveying the sea surface at a grazing angle of 4.7. The Pareto distribution has appeared within last decade in radar signal processing as an alternative to K-distribution. This model was first examined in the context of modelling sea clutter returns at X-band.