This paper explicates how Orem's Self-care Deficit Theory of Nursing (Orem, 1995) was selected to guide a study to explore and measure cancer related fatigue (CRF), and determine the most effective self-care strategies used to combat CRF in a cohort of patients with a diagnosis of cancer (breast cancer, colorectal cancer, Hodgkin's and Non-Hodgkin's lymphoma). The secondary aim was to explore self-care agency and its relationship to CRF.