Hypertensive emergencies in hemodialysis require immediate therapy, usually by parenteral drug administration; however, sublingual medications may have potential in this special condition. Sublingual captopril (25 mg), nifedipine (10 mg) and prazosin (2 mg) were prescribed to determine the effectiveness and safety of each medication in the treatment of hypertensive emergencies during hemodialysis. Blood pressure and heart rate were measured continuously up to 120 min postdose. The response rates were 83% for captopril, 90% for nifedipine and 11% for prazosin. The significant hypotensive effects of both sublingual captopril and nifedipine occurred at 10 min and continued up to 120 min. The reduction of systolic blood pressure occurred earlier in nifedipine than captopril (10 vs. 15 min). No significant difference in heart rate between them was noted. There were no side effects in the captopril group but flushing, tachycardia and headache were observed in 4 patients of the nifedipine group. We concluded that sublingual captopril and nifedipine were effective but captopril seemed to have less side effects than nifedipine and may be an excellent alternative to sublingual nifedipine in the urgent treatment of hypertensive emergencies in hemodialysis. Prazosin was not recommended because of its low response rate.