Improvement of the model systems.

of recognizing an important correlation if we obtained one. Nevertheless, I contend that much has been learned about cancer and cancer chemotherapy—at the molecular level, the cellular level, the animal tumor level, and the clinical level. We may even be approaching a point when objective interdigitation of what we have learned from many model systems can lead to more rational and efficient application. One of our biggest problems may turn out to be "unlearning" some of what we thought we knew but didn't know at all. By