The authors assessed whether measurements obtained by Judkins-style Doppler catheters are comparable to those achieved with the intracoronary Doppler technique in 42 patients with normal coronary arteries on angiography (19 syndrome X and 23 heart transplant patients). Resting coronary flow velocity and response to a hyperemic intracoronary dose of papaverine was measured with a Judkins-style, 8F Doppler-tipped catheter positioned in the left coronary ostium and a 3.6F intracoronary Doppler catheter positioned in the proximal left anterior descending artery. Mean coronary flow velocity at rest was significantly higher with the Judkins Doppler (10.1 +/- 4.6 vs 6.3 +/- 4.5 cm/sec, p < 0.01). The mean coronary flow velocity at peak hyperemia was also significantly higher with the Judkins Doppler (33.7 +/- 14.1 vs 19.7 +/- 11.5 cm/sec, p < 0.01). Coronary flow reserve was 3.57 +/- 1.3 with the Judkins Doppler and 3.47 +/- 1.2 with the intracoronary Doppler (r = 0.85). A second study was performed in 14 heart transplant patients with the intracoronary Doppler positioned in the left main coronary artery. The resting and hyperemic flow velocities were again higher with the Judkins Doppler but the differences were not statistically significant. There was again a strong correlation between the Doppler catheters for coronary flow reserve measurements. The Judkins-style Doppler technique appears to be a quick, safe, and accurate alternative to the intracoronary Doppler technique.