A theoretical procedure for estimating the precision of the T 1 Fast Acquisition Relaxation Mapping sequence as a function of a number of acquisition parameters has been validated by both simulations and experimental results. These results have clarified the selection of sequence parameters to give optimal accuracy and precision in the R 1 * measurements. There is excellent agreement between theory, simulation, and experiment except for flip angles greater than 9 o , at which point slice profile imperfections significantly degrade the precision of the technique. The experimental results indicate that over a range of T 1 s that would be seen in a bolus tracking experiment (25-1200 ms), T 1 Fast Acquisition Relaxation Mapping can be used to obtain 64 x 128 R 1 * maps at a rate of 1 map/s, with a precision of 10% or better.