Obtaining diffraction quality crystals is frequently an iterative process which traditionally has involved screening large numbers of crystallization conditions. Due to advances in high-throughput gene engineering, recombinant expression, and purification, the protein of interest has now become one of the many variables routinely investigated during crystallization trials. As such, construct design is a critical step in the path toward successful crystallization. In this chapter will we address construct design strategies frequently employed to improve the solution and crystallization behavior of proteins. Topics covered include choosing a recombinant expression system and reducing disorder through truncations and surface mutagenesis. Also covered are strategies to reduce heterogeneity from posttranslational modifications, impurities, and aggregation.