Serum lipids and lipoprotein concentrations have been associated with dominance aggression in humans. The aim of this study was to investigate the link between serum lipids, including cholesterol, triglyceride, high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), total cholesterol (TC) to HDL-C ratio and dominance aggression in dogs. Levels of serum TC, triglyceride and HDLC were significantly lower in dogs with dominance aggression compared with non-aggressive dogs (P < 0.001). These results suggest that a relationship exists between serum lipid pro. le and dominance aggression in dogs, and hypocholesterolaemia exists in dogs with dominance aggression.