Protein engineering techniques can facilitate the direct de-convolution of specific domains, regions, and particular amino acids that contribute to protein function. Many tools are available to aid this enterprise and herein we describe one such tool, a technique we term "Molecular Scanning" (MS). MS is analogous to previously described alanine scanning in that it samples potentially functional sequence space, but differs in that it uses Error-Prone polymerase chain reaction to randomly introduce all amino acids across the sequence space, as opposed to simply introducing alanine at each desired position. We commonly use MS in conjunction with ribosome-display, selecting for specific character traits (e.g., improved affinity) which allows us to sample functionally relevant diversity on a reasonably large scale. This approach is amenable to a variety of different mutational techniques and display technologies as dictated by user requirements or needs. In this chapter we present a general outline of the process as we have previously successfully applied it.