The conserved-vector-current hypothesis, together with measured nuclear beta-decay rates, predicts a value of the rate for the decay ..pi../sup +/..--> pi../sup 0/e/sup +/..nu.. of 0.4027 +- 0.0018 s/sup -1/. Using a decay-in-flight technique we have made the most precise measurement to date of this rate, obtaining the value 0.394 +- 0.015 s/sup -1/, in good agreement with the prediction. This differs slightly from the value previously reported in W. K. McFarlane et al., Phys. Rev. Lett. 51, 249 (1983).