Values of stroke distance obtained from 25 subjects with the obsolete Transcutaneous Aortovelograph were compared with those from two commercially available Doppler ultrasound devices, the Doptek Decoder, and the Doppler unit of the Interspec-XL Ultrasound System. Also studied was the Quantascope, an ultrasound device designed to measure stroke volume. In the aortic arch, reproducibility was 4.8% with the Transcutaneous Aortovelograph, 9.1% with the Doptek Decoder, 17.2% with the Interspec, and 23.6% with the Quantascope. In the ascending aorta, reproducibility was worse, being 13.4% for the Doptek, 23.0% for the Interspec, and 28.1% for the Quantascope. There was close agreement between the absolute values of stroke distance obtained with the Transcutaneous Aortovelograph and the Interspec, but lower values were obtained by the Doptek Decoder. There is a need for an updated instrument dedicated to the measurement of stroke distance in the aortic arch.