The large flare of August 18, 1979 resulted in a shock which produced intense type II radio emission detected at kilometer wavelengths using the radio astronomy experiment on the ISEE-3 spacecraft. The drift rate of the type II burst provides estimates of the velocity of the shock as a function of coronal height. A choice of density scale has been facilitated by detection of the shock with radio scattering measurements using the radio signals from Voyager 1 and Pioneer 11. Assuming radial motion of the shock, the spacecraft detections provide estimates of the arrival times of the shock at 13 R⊙ and 73 R⊙. The arrival time of the shock at ISEE-3 and subsequently at the magnetosphere can also provide estimates of the shock velocity. The resulting profile of velocity as a function of distance is consistent with the shock being driven out to about 0.2 AU and then decelerating with a decreasing outward speed proportional to R-0.8. The profile presents the first determination of the velocity characteristics of a flare-produced shock in the height range 0.05--0.4 AU.