This paper traces the origins of Biometeorology and Medical Bioclimatology, from Hippocrates, through a slow evolutionary path, until the 70s of the last century. These disciplines, yet little known to the medical profession, are to be framed in the context of environmental sciences applied to epidemiology, with significant operational impacts in terms of prevention. After a brief description of the subject and climatic factors (variables), we draws a picture of the technical and scientific initiatives recently implemented especially by the WHO, and then explore the broad spectrum of scientific research, carried out especially in the last two decades, which have consolidated multiple knowledge. Finally, we examine briefly the meteorological event of Summer 2003 as a specific case, its epidemiology and the consequent initiatives of Hygiene and Public Health developed by Italy and other countries.