Professor Martin Pall Professor School of Molecular Biosciences WWAMI Program Washington State University Pullman Dr. Pall has long-term interests in biological regulatory mechanisms. His current research is focussed on a theory he has developed on the cause (etiology) of chronic fatigue syndrome and the overlapping and related conditions of multiple chemical sensitivity, fibromyalgia, and posttraumatic stress disorder. According to this theory, each of these is initiated by stresses that induce increased levels of nitric oxide and its oxidant product peroxynitrite, followed by a biochemical vicious cycle mechanism associated with chronic elevation of these two compounds. Symptoms of these conditions are produced by both nitric oxide and peroxynitrite and treatment should focus on downregulating this vicious cycle mechanism. Vitamin B-12 injections commonly used to treat these conditions are proposed to act through the action of one form of B-12 (hydroxocobalamin) which is a potent nitric oxide scavenger. Dozens of biochemical and physiological observations provide support for this theory. The most puzzling features of these conditions are explained by this novel theory.