The "mosaic of autoimmunity" describes the multifactorial origin and diversity of expression of autoimmune diseases in humans. The term implies that different combinations of the many factors that are involved in auto-immunity produce varying and unique clinical pictures in a wide spectrum of autoimmune diseases. Most of the factors involved in autoimmunity can be categorized into four groups: genetic, immune defects, hormonal and environmental factors. In this communication, only the environmental factors are reviewed such as: infectious agents (represented by Epstein-Barr virus and cytomegalovirus), vaccines as triggers of autoimmunity, smoking and its relationship with rheumatoid arthritis, systemic lupus erythematosus, thyroid disease, multiple sclerosis and inflammatory bowel diseases. Some aspects of stress as implicated in causing autoimmunity and the processes leading to autoimmunity are reviewed as well.