Intrinsic chemical instability and physical instability of therapeutic proteins require appropriate formulations and processes to ensure their efficacy and safety. Recent concerns on possible immunogenicity of the structurally altered protein molecules emphasize relevance of the product quality. Advances in the protein and material researches enable rational design of the aqueous solution and solid protein formulations. This chapter describes the basic process to develop the formulations and choice of excipients that protect the proteins from various stresses during the manufacturing and storage.