Propranolol is a commonly used drug; of new and refilled prescriptions, it ranked no. 1 in 1984 and no. 2 in 1985. Medical conditions for its use include angina pectoris, myocardial infarction, hypertension, cardiac dysrhythmias, hypertrophic subaortic stenosis, migraine headache, hyperthyroidism, and pheochromocytoma. Almost all dental practitioners will treat a patient receiving propranolol for one of these conditions. The following recommendations seem appropriate at this time: The patient should continue to receive propranolol during dental treatment. Sudden withdrawal of the beta-blocker will cost the patient the benefit of propranolol therapy and may lead to acute myocardial ischemia. Acute stress should be minimized, as hypertensive responses may also be caused by endogenously released epinephrine. Short appointments scheduled in the morning, possibly with conscious sedation, should be considered. The dosage of adrenergic vasoconstrictors should be limited and gingival retraction cord containing epinephrine avoided entirely. The blood pressure should be taken approximately 5 minutes after local anesthesia is administered to determine if a systemic response has occurred. In the unlikely event of a hypertensive emergency, a rapidly acting, short-duration antihypertensive drug, such as the alpha-blocker phentolamine (Regitine, 5 mg intravenously) should be administered. Sublingual nitroglycerin (Nitrostat, 0.4 mg) may be useful as a nonparenteral alternative. These recommendations apply to other nonselective beta-blockers, including nadolol (Corgard) and timolol (Blocadren). They may also apply to labetalol (Normodyne, Trandate), a nonselective beta-antagonist with some alpha-blocking activity and to pindolol (Visken), a beta-blocker with some intrinsic beta 2-agonistic activity.(ABSTRACT TRUNCATED AT 250 WORDS)