The current issue of The Lancet Neurology features an article on the PET assessment of changes in amyloid load in patients with Alzheimer's disease treated with bapineuzumab. Rinne and collegues report something of a breakthrough by demonstrating the feasibility of eventually testing the so-called amyloid hypothesis of sporadic Alzheimer's disease in vivo. The study finds that treatment with bapineuzumab for 78 weeks reduced cortical 11C-PiB retention compared with both baseline and placebo. 11C-PiB PET seems to be useful in assessing the effects of potential Alzheimer's disease treatments on cortical fibrillar amyloid-β load in vivo.