Context The healthy ageing assumptions may lead to substantial changes in paths of aggregate healthcare expenditures, notably catastrophic expenditures of people at the end of the life. But clear assessments of involved amounts are not available when we specifically consider ambulatory care (as drug expenditures) generally offered to chronically-ill people who can remain in this health-status for a long time onward. The Government and Social Security need tools to predict the future cost of health in particular drugs expenditures taking account epidemiological changes on future. This study estimates the evolution in reimbursable outpatient drug expenditures, attributable to age structure and chronic conditions changes, of the French populat...