Recent epidemiological reports suggest that statins, and possibly other lipid lowering agents, might be protective for Alzheimer disease, and for other types of dementia. Importantly, however, epidemiological reports of this type are susceptible to indication bias, i.e. people who elect to take lipid-lowering agents might be healthier than those who do not, so that it may be these other health factors which explain their lower risk of dementia. Limited clinical trials data support the notion that statins, in particular, have important effects on cerebral cholesterol metabolism, but the link to clinical effects in dementia has yet to be established, and the mechanisms by which lipid lowering agents might confer protective effects is unclear. Dedicated clinical trials are now under way, and their results are awaited with great interest.