Agouti and Agouti-related proteins are important signal proteins involved in the regulation of the melanocortin receptor signaling.Aberrant or ectopic expression of these proteins has been shown to cause abnormal coat color pigmentation and development of obesity,diabetes and tumors.A number of mouse models carrying mutations for agouti or agouti-related proteins are being utilized to study the underlying pathogenic mechanisms for a number of important human diseases.This review attempts to summarize a few aspects of important research progress in this area.