The International Atherosclerosis Project (IAP) quantified atherosclerosis of the aorta and coronary arteries in over 31,000 persons age 10 to 69 who died between 1960 and 1965 in fifteen cities and countries throughout the world. The IAP established that the average severity of atherosclerosis differed widely in many parts of the world and that the differences correlated with mortality from ischemic heart disease. It also demonstrated that the fatty streaks of childhood were prevalent and severe in both boys and girls. Fibrous plaques generally first appeared between the ages of 20 and 30 and in proportion to the prevalence of ischemic disease in the adult population. Since the results of the IAP were first published in 1968, research into atherosclerosis has changed greatly from gross and microscopic morphological methods to manipulation of experimental animals, in vitro culture of arterial wall cells, and the application of micro-chemical, physical chemical, and immunological techniques to tissues.