Modifications in cellular membranes can be observed in aging and Alzheimer's disease (AD). These mainly concern the degree of the membrane's viscosity, with consequent reduction of the activity of some protein structures, such as enzymes, receptors and membrane carriers. Moreover, dendritic spine loss, found in aging- and AD brain, is one of the most characteristic findings. The BC-PS, a phospholipid, purified from bovine brain, is found to be able to influence positively the above cited modifications. Moreover, BC-PS administration to old rats improves the performances in some memory tests. In humans, the effects of BC-PS have been studied by some controlled trials in AD and related cognitive disorders. The most recent of these trials, conducted on an Italian population of AD patients is presented here, emphasizing in particular its methodological aspects.