This book is dedicated to development of an intelligent information system of diagnosis and monitoring of poisoning by toxic substances with the use of carbon monoxide as an example. The cases of carbon monoxide poisoning occupy the third place by their incidence and occurrence after cardiovascular and oncological diseases. The application of information technologies is due to complexity, indetermination and a great quantity of parameters in the problem under consideration. A class of toxic substances is revealed which cause symptoms similar to those of carbon monoxide poisoning thus bringing confusion and difficulties to diagnosing poisoning by the latter. Carbon monoxide poisoning has severe consequences, after some time a patient affected by carbon monoxide develops neurosomatic and cardiovascular diseases, cardiac muscle injury may lead to myocardial infarction and even death. For this reason construction of an intelligent information system is proposed with diagnosis and monitoring of the state of carbon monoxide poisoning. Such systems can be used in conditions ambulances and dynamic control.