β-Casomorphin (1-4), amide (bovine) is a potent and specific agonist for morphine (μ) receptors. β-Casomorphin (1-4), amide (bovine), as a synthetic peptide, is the amide of a fragment of the milk protein β-casein. β-Casomorphin (1-4), amide (bovine) has morphinelike activities and is highly specific for morphine (μ) receptors but not for enkephalin (⸹) receptors.