Revised pattern analysis (RPA) is a stepwise algorithmic method for the diagnosis of pigmented skin lesions, pigmented by melanin, significant blood pigment (as in structureless blood or red clods), or discolored keratin. Revised pattern analysis uses a limited number of clearly defined geometric terms and provides a clear stepwise process of analysis, assessing patterns then colors and finally clues, leading the clinician to a specific provisional diagnosis or alternatively a limited differential diagnosis. In the language of RPA, there are five basic structures. Pattern of lines, pattern of pseudopods, pattern of circles, pattern of clods, and pattern of dots are the basic structure, which are briefly explained in this chapter along with their images.