Recent research has shown a widening gap in life expectancy at age 50 between the U.S. and Europe, as well as large differences in the prevalence of diseases at these ages. Little is known about the processes determining international differences in the prevalence of chronic diseases. Higher prevalence of disease could result from either higher incidence or longer disease-specific survival. This paper uses comparable longitudinal data from 2004 and 2006 for populations aged 50 to 79 from the U.S. and a selected group of European countries to examine age-specific differences in prevalence and incidence of heart disease, stroke, lung disease, diabetes, hypertension, and cancer as well as mortality associated with each disease. Not surprisingly, it finds that Americans have higher disease prevalence. However, incidence of most diseases and survival conditional on disease is higher in Europe at older ages, in particular after age 60. The survival advantage in Europe tends to disappear when we control for co-morbidities but does not suggest a survival advantage in the U.S. Therefore, the origin of the higher disease prevalence at older ages in the U.S. is to be found in higher incidence and prevalence earlier in the life course.