The invention relates to methods of enhancing normal melanocortin-4 receptor (MC4R) activity, and to enhancing activity of an MC4R having a mutation which affects protein folding and/or processing of the MC4R. The invention provides a method of treating an individual having a condition in which increased activity of an MC4R at the cell surface would be beneficial, for example in obesity, by administering an effective amount of a pharmacological chaperone for the MC4R. The invention provides MC4R pharmacological chaperones which enhance the activity of MC4R. The invention further provides a method of screening to identify pharmacological chaperones which enhance folding of an MC4R in the endoplasmic reticulum (ER), in order to enhance the activity of the MC4R at the cell surface.