We report measurements of ~150 keV proton intensity enhancements obtained at ACE and WIND when both spacecraft were upstream of the Earth's bow shock. We investigate differences in the onset times, the duration's, and the local magnetic field orientations for 4 events observed simultaneously at the two spacecraft. A simple statistical analysis shows only 2% of the simultaneous events could be random coincidences, which indicates that out of the 20 events observed at each spacecraft, the 4 simultaneous measurements are probably observations of the same events. Since these measurements were obtained when the two spacecraft were separated by distances >25 RE, these particles probably originate from a source region that possibly covers the scale size of the Earth's bow shock (~10 RE), and this is substantially larger than the smaller source regions proposed by existing models. ¿ 1999 American Geophysical Union