This report focuses mainly on the major reduction of the risk of relapse of gastrointestinal stromal tumor (GIST) treated with imatinib, as identified in the American College of Surgeons Oncology Group (ACOSOG) Z9001 trial. It also focuses on the many unknowns associated with adjuvant imatinib therapy despite approvals by the US Food and Drug Administration and the European Medicines Agency, and on a new marker for the diagnosis of GIST.