The present invention relates to methods of generating highly concentrated protein solutions, e.g., an antibody solution, a therapeutic protein solution, etc. The methods of the invention include membrane evaporation, such as evaporation of protein-free solvent from the protein solution, which concentrates the protein. The methods of the present invention result in protein solution concentrations not previously achievable by conventional ultrafiltration methods, e.g., protein solution concentrations of greater than about 260 grams of protein per liter of solution.