Millions of patients suffer from Alzheimer's disease, and intensive efforts to find a cure for this devastating disorder center on the proteases, which release the deadly amyloid β-peptide from its precursor. The cutting procedure is thought to be cholesterol dependent and strategies to lower cholesterol as therapeutic treatment are under intensive investigation. Recent findings suggest that the complete proteolytic machinery required for amyloid β-peptide generation is located within lipid rafts. Data by Dotti and colleagues (Abad-Rodriguez et al., 2004), in this issue, suggest that rafts isolate the cutting machinery away from its deadly substrate. These findings describe a novel mechanism for controlling proteolytic activity by building a lipid boundary between proteases and their substrates.