Dr. James Martenson, Jr. is a Professor of Oncology, Mayo Clinic College of Medicine and is a consultant in the Department of Radiation Oncology. Dr. Martenson is also the Research Base Scientific Co-Coordinator for GI Malignancies for the North Central Cancer Treatment Group.

Dr. Martenson's principle research effort involves clinical trials in patients with gastrointestinal cancer and supportive care of the cancer patient, particularly those receiving radiation therapy. Most of his research is done through cooperative groups, particularly the North Central Cancer Treatment Group.