Protein properties are highly diverse, making parallel expression and purification a particular challenge. Parallel methods are typically used when a number derivatives of a target protein are desired or when multiple homologs are needed. A typical scenario involves target evaluation, cloning and mutagenesis of the target, expression screening, large-scale expression and purification, and analytical and biophysical testing of the resulting protein. This chapter describes some of the strategies and methods employed for parallel protein expression and purification.