We use Yohkoh soft X-ray telescope (SXT) images of eruptive events visible against the solar disk to examine the coronal structures and the boundaries of the large-scale magnetic fields considered to be involved in coronal mass ejections (CMEs). From an initial list of about 100 large-scale events we selected five for detailed study. The transient X-ray structures in these events spanned distances across the solar surface ranging from 35 to >100 heliographic degrees, comparable to the spans of white light CMEs observed at the limb. The widths of the coronal loop arcades spanned two or three neutral lines, or a single, highly convoluted neutral line. Our interpretation of these results is that multipolar magnetic systems are a common configuration of the source fields of many CMEs, contrary to the first-order approximation that CMEs involve the eruption of simple, bipolar structures.¿ 1997 American Geophysical Union