A double blind, placebo controlled trial of nicardipine in the treatment of high Doppler Flow Velocity (DFV) following severe head injury (Glasgow Coma Score (GSC) less than or equal to 8) was performed. Thirty patients with high DFV (greater than or equal to 100 cm/s for 6 h duration) on transcranial Doppler ultrasound, were treated with nicardipine or placebo for 24 h (2.5 mg/h, increasing in steps of 2.5 mg/h at 2 h intervals (maximum rate 7.5 mg/h) depending on response of DFV). DFV was measured hourly for 24 h and then every 12 h for 2 days. Nicardipine significantly reduced DFV below the threshold of 100 cm/s (16/19 cf placebo 3/11, chi-square p less than 0.001). In the nicardipine treated group maximum DFV was significantly reduced (p less than 0.001) and time with DFV below 100 was significantly longer. Rises in DFV were significantly reduced by the drug if the DFV was normal at the time of entry. High DFV returned on cessation of the infusion. No unexpected or adverse side effects were seen. No clinical benefit was demonstrable.