A technique widely used in radio astronomy to enhance maps from interferometers. It consists of a series of steps to identify and remove the effect of distortion caused by unwanted side lobes. The distortion (i.e. the side-lobe pattern) can usually be calculated or measured for a particular interferometer. The technique is particularly useful for producing good maps from aperture synthesis observations in which only a fraction of the total aperture has been synthesized. The raw, or dirty, maps contain numerous false features caused by the side lobes. The CLEAN technique recognizes true features and separates them from the side-lobe pattern.