A man has two episodes of demonic possession several years apart. His detailed experiences are analyzed from a psychological, psychological, historical, parapsychological and cross-cultural perspective. Signs and symptoms of demonic possession mimic mental illness. Ruling out mental illness is prerequisite for an exorcism. A detailed psychological analysis is explored to arrive at the proper diagnosis, i.e. differentiating mental illness and demonic possession. The criterion used by the Catholic Church to diagnosis possession such as revealing hidden knowledge, speaking or understanding a foreign language unknown to the possessed, abnormal strength, levitation, telepathy and psychokinesis are explained. Deliverance ministries are dealt with skeptically but are provided guidelines. Ministers and counselors are provided information on discernment to help identify demonic possession. Occult practitioners and Satanists are discussed relevant to demonic possession. Novel experiments with electromagnetic equipment are used to accommodate and disrupt demonic possession. Bioelectrical energy, electromagnetic energy, geomagnetic fields and ectoplasmic demonic energy are delineated. Psychological treatment strategies are provided for counselors, demonically possessed and those who are diagnosed with mental illness.