The hypothesis that Natural Genetic Engineering (NGE) is at the root of diseases of immune pathology - autoimmune diseases - was first mooted in Pease's first book "L-Forms, Episomes and Auto-Immune Disease," published in 1965, and the idea that the properties of an organism could be altered by DNA carried by bacteria or viruses as vectors entering their cellular genetic processes was generally regarded as unacceptable. Shortly afterwards, however, it was confirmed that such mechanisms do occur in nature, in plant and animal cancers. It was further discovered that these natural transfers could be replicated in the laboratory, and laboratory genetic engineering (LGE) became a reality. "Aids, Cancer and Arthritis" reviews the advances made to support Dr. Pease's NGE theory in immune diseases, notably in tissue typing and the association of certain tissue types with certain human disorders. A chapter on human, animal and plant malignancies has also been included. The almost universally accepted belief that HIV is the sole cause of AIDS is analysed dispassionately and it is concluded that current thinking is far too simplistic, and that AIDS could in fact be autoimmune in nature. The implications of this for vaccine preparation and therapy are discussed.