The idea that coronal mass ejections (CMEs) originate from the evolution of the large-scale solar field and in particular arise from regions of freshly opening coronal flux is reexamined using a new approach. Potential field models constructed from Wilcox Solar Observatory magnetograms are applied to study both the rate of opening of coronal fields with time and the locations of observed CMEs compared to the inferred newly open field regions on the Sun. Case studies are drawn from SMM coronagraph data. Yohkoh soft X ray images, and counterstreaming electron events observed on the ICE spacecraft. The results suggest that the large-scale field evolution paradigm of CMEs deserves further attention and has potential for applications to space weather forecasting. ¿ 1998 American Geophysical Union