Serum proteins consist of albumin and globulins. Fibrinogen is present in plasma but not in serum. Differential analysis of plasma proteins can be done by chemical precipitation methods and physical methods like electrophoresis, ultra-centrifugation, isoelectric focusing, immunological methods, etc. This chapter covers the biuret method and other methods of protein estimation. Other methods of protein estimation are Kjeldahl’s method, lowry method, dye-binding methods, direct photometric method, refractometry, and turbidimetric and nephelometric method briefly explained.