Treatment approaches for patients with chronic fatigue syndrome (CFS), Myalgic Encephalomyelitis (ME) and Myalgic Encephalomyelitis/chronic fatigue syndrome (ME/CFS) have been controversial. This paper provides the theoretical and conceptual background for the Energy Envelope Theory to assist patients and reviews evidence of its treatment efficacy. Over a 15-year period, efforts were directed to develop a non-pharmacologic intervention that endeavored to help patients to self-monitor and self-regulate energy expenditures and learn to pace activities and stay within their energy envelope. Studies show that the energy envelope approach, which involves rehabilitation methods, helps patients pace activities and manage symptoms and can significantly improve their quality of life.