During July and August, 1958, a total of 20 wind observations was made at altitudes between 100,000 and 300,000 ft at Johnston Island in the Pacific Ocean. In addition, three observations were made at Tonopah, Nevada in May 1958. These measurements resulted from radar tracking of chaff expelled from rockets. A height profile of the measured winds is presented, and a description of the two-stage rocket-delivery system is given. Observed winds were predominantly and consistently easterlies with average speeds near 75 kn. Little change with altitude was noted, although there are indications of reversal of direction to westerlies above 300,000 ft. System errors are discussed. Also, an attempt is made to determine 12- and 24-hourly periodicities in these data; results are inconclusive, however, because of data scarcity.