The contractile effects of substance P and human calcitonin gene-related peptide (human CGRP) on isolated human intracervical arteries were studied. Human cervical tissue specimens were excised after hysterectomy at various phases of the menstrual cycle (n = 14) and small intracervical arteries were dissected free by microtechnique. Ring preparations of the vessels were prepared and mounted in organ baths, and isometric circular tension was recorded. Neither compound affected resting tension. Both peptides showed potent relaxing effects on vessels precontracted by noradrenaline 10––5M. Substance P exhibited the higher potency, while human CGRP showed the higher efficacy. The relaxing effects of the two compounds were unaffected by pretreatment with indomethacin 10––6M, propranolol 10––6M and atropine 10––6M. The results support a role for the two peptides in the regulation of cerv