Invited response to definition of hormesis (EJ Calabrese and LA Baldwin).

Calabrese and Baldwin have proposed the Theory of Hormesis to explain a variety of disparate data. We evaluated the explanation using examples of pulmonary injury, radiation injury to white blood cells and selenium as an essential element, reducer of carcinogenesis and a potential toxicant. Calabrese and Baldwin have fulfilled many of the criteria allowing generalizability of their theory. They have gathered data extensively. These data were logically consistent with their experiences. They needed to examine critically the theory and any theories competing with it. At this point, each theory must be proved, disproved or its limitations clearly stated. It is in this phase that most work is still being accomplished. This examination is important because it provides referents for vigorous outside criticism, the final phase. Calabrese and Baldwin are to be complimented on seeking outside comment. Considerable refinement of the theory has taken place with time.