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We evaluated methods for measuring average and regional pulse-wave velocity along the full length of the aorta in 18-mo-old ether-anesthetized male spontaneously hypertensive rats. Catheter-tip manometers were placed in the ascending and descending thoracic aorta via the right carotid and left femoral arteries, respectively. As the distal catheter was withdrawn at 1-cm intervals, the relationship between the distal catheter insertion distance and distance between transducers was determined from the intercept of the insertion distance vs. transmission delay regression line. Methods that assessed the foot-to-foot time delay between pressures accurately predicted the separation between catheters (measured distance of 1.43 cm; intercept of 1.40 +/- 0.5 cm; P = not significant) were highly reproducible (coefficient of variation of 2.3% for repeated measurements) and showed minimal variability (range 509 +/- 30 to 600 +/- 29 cm/s) along the full length of the aorta. Methods that made use of the pressure-pressure transfer function were spatially (range of values along the aorta 367 +/- 17 to 722 +/- 39 cm/s) and temporally more variable, especially during vasoconstriction with methoxamine, due to the effects of reflected waves.