The use of sustained release tri-iodothyronine (SR-T3) in clinical practice, has gained popularity in the complementary and alternative medical community in the treatment of chronic fatigue with a protocol (WT3) pioneered by Dr. Denis Wilson. The WT3 protocol involves the use of SR-T3 taken orally by the patient every 12 hours according to a cyclic dose schedule determined by patient response. The patient is then weaned once a body temperature of 98.6 degrees F has been maintained for 3 consecutive weeks. The symptoms associated with this protocol have been given the name Wilson's Temperature Syndrome (WTS). There have been clinical studies using T3 in patients who are euthyroid based on normal TSH values. However, this treatment has created a controversy in the conventional medical community, especially with the American Thyroid Association, because it is not based on a measured deficiency of thyroid hormone. However, just as estrogen and progesterone are prescribed to regulate menstrual cycles in patients who have normal serum hormone levels, the WT3 therapy can be used to regulate metabolism despite normal serum thyroid hormone levels. SR-T3 prescription is based exclusively on low body temperature and presentation of symptoms. Decreased T3 function exerts widespread effects throughout the body. It can decrease serotonin and growth hormone levels and increase the number of adrenal hormone receptor sites. These effects may explain some of the symptoms observed in WTS. The dysregulation of neuroendocrine function may begin to explain such symptoms as alpha intrusion into slow wave sleep, decrease in blood flow to the brain, alterations in carbohydrate metabolism, fatigue, myalgia and arthralgia, depression and cognitive dysfunction. Despite all thermoregulatory control mechanisms of the body and the complex metabolic processes involved, WT3 therapy seems a valuable tool to re-establish normal body functions. We report the results of 11 patients who underwent the WT3 protocol for the treatment of CFS. All the patients improved in the five symptoms measured. All patients increased their basal temperature. The recovery time varied from 3 weeks to 12 months.