A drug needs to be formulated in a safe, consistent, and stable dosage form with proven clinical efficacy before it can be approved for specific therapeutic indications by drug regulatory authorities. Depending on the modes of chemical degradation or physical denaturation, a wide variety of formulation excipients or additives, including buffers, antioxidants, sugars, and polysaccharides, can be used to preserve the structural integrity and biological activity of such vulnerable macromolecules. This article focuses on the stability problems of biopharmaceuticals and their assessment as well as the formulation approaches that can be used to circumvent these problems.