To reveal the molecular basis of fever initiation, we examined lipopolysaccharides (LPS)-induced fever model in monoacylglycerol lipase (MGL)-deficient (Mgll−/−) mice, CB1 receptor-MGL compound-deficient (Cnr1−/−Mgll−/−) mice, cytosolic phospholipase A2α (cPLA2α)-deficient (Pla2g4a−/−) mice, and diacylglycerol lipase α (DGLα)-deficient (Dagla−/−) mice. The gene discussed is CNR1; the disease is Fever.