For the years 1969-1978, the authors studied the pattern of mortality resulting from cardiovascular diseases (390-438 International Classification of Diseases [ICD]), ischemic heart diseases (410-414 ICD), and cerebrovascular diseases (430-438 ICD), and then correlated mortality rate with water hardness. The study took place in the region of Abruzzo, Italy, which has a population of 594,323. An inverse correlation between drinking water hardness and mortality due to cardiovascular disease, already reported by other authors in many countries, is also confirmed in this research for the disease group 390-438 and for the group of individuals aged 45-64 yr.