Three novel opioid agonists are described. These compounds were found to bind with high affinity and selectivity to the kappa-opioid receptor. Isolated tissue studies using the field-stimulated mouse vas deferens and guinea-pig ileum preparations confirmed the high agonist potency and naloxone-reversibility of these agents. All three compounds exhibited potent antinociceptive activity in the mouse abdominal constriction model. These compounds should prove useful as tools to investigate kappa-receptor function.