The scale of the global cost of dementia is explainable when one considers that around 0.5% ofthe world?s total population live with dementia.? A high proportion of people with dementia need some care, ranging from support withinstrumental activities of daily living (such as cooking or shopping), to full personal care andround the clock supervision. Costs are lower in developing countries, both per person and societally (as a proportion ofGDP). In these regions, there is a much greater reliance on the unpaid informal care provided byfamily and others. Worldwide, the costs of dementia are set to soar. We have tentatively estimated an 85%increase in costs to 2030, based only on predicted increases in the numbers of people withdementia. Costs in low and middle income countries are likely to rise faster than in high incomecountries, because, with economic development, per person costs will tend to increasetowards levels seen in high income countries, and because increases in numbers of peoplewith dementia will be much sharper in those regions. There is an urgent need to develop cost-effective packages of medical and social care thatmeet the needs of people with dementia and their caregivers across the course of the illness,and evidence-based prevention strategies. Only by investing now in research and cost-effectiveapproaches to care can future societal costs be anticipated and managed. Governments andhealth and social care systems need to be adequately prepared for the future, and must seekways now to improve the lives of people with dementia and their caregivers.