Objective: This study was designed to show the effects of sublingually administered nifedipine and captopril on middle cerebral arterial blood flow during hypertensive crisis in the emergency department. Methods and results: Transcranial Doppler ultrasonography (TCD) was performed on the patients fulfilling the criteria (15 patients given captopril, 13 patients given nifedipine, mean (+/-SD) age 56 +/- 11 and 54 +/- 10 years, respectively). Then, patients were randomized into sublingually administered captopril or nifedipine groups and after the drug administration, TCD was repeated. Initial systolic and diastolic blood pressures were 200 +/- 21/125 +/- 21 mmHg in the captopril group and 199 +/- 17/123 +/- 20 mmHg in the nifedipine group. There was no significant difference between antihypertensive effects of the drugs after initiation of treatment. Before the treatment with captopril, middle cerebral artery (MCA) flow velocities (Vm) and pulsatility index (PI) were 76.74 +/- 6.38 cm/s and 1.18 +/- 0.09, respectively. The values after the treatment with captopril were 78.21 +/- 15.24 cm/s (p < 0.05) and 0.92 +/- 0.08 (p < 0.001), respectively. Before the treatment with nifedipine, Vm and PIS were 64.73 +/- 5.11 cm/s and 1.14 +/- 0.18, respectively. After the treatment with nifedipine, Vm was 60.04 +/- 5.36 cm/s (p < 0.01) and PI was 1.21 +/- 0.09 (p < 0.01). Conclusion: After treatment with captopril, PIs were decreased to normal limits but in the group treated with nifedipine, PIs increased to more pathological values. These results showed that we should reconsider the use of nifedipine in the emergency departments as an antihypertensive agent in hypertensive attack treatment.