Diffusion of medical technology and the growing proportion of elderly people in the population are generally regarded as major contributors to the increasing health care expenditure in the industrialised world. This study explores the importance of one specific factor in this process, the change in the use of technology among elderly patients. In some instances, a new technology is first used among younger patients and then gradually extended to the elderly. Two such cases are studied, both representing costly procedures: coronary bypass surgery (treatment of coronary heart disease) and dialysis (treatment of uraemia). In both cases, we demonstrate significant diffusion to older age groups. It is also tentatively concluded that the diffusion of technology could have an important effect on per capita health care expenditure among the oldest of the old. © 2001 Elsevier Science Ltd. All rights reserved.