Alzheimer's disease (AD) is a neurodegenerative disease caused due to aggregation of A beta peptides in the brain tissues. Recently, several studies on AD transgenic mice have shown the effect of caffeine in significantly reducing the A beta amyloid level in their brains. However, the mechanism and mode of caffeine action on amyloid aggregation are not known. Therefore,, in this study,, we have carried out molecular dynamics simulations of five amyloicl-fOrming 16-22 peptides in pure water and in a regime of caffeine solutions, with different caffeine/peptide stoichiometric ratios. The secondary structure analyses _of peptides in pure- water show the formation of fl -sheet conformations, whereas on addition of caffeine, these ordered conformations become negligible. The radial distribution function, contact map, nonbonding interaction energy, hydrogen bonding, potential of mean force, and hydration analyses show. that there is less interpeptide interaction in the presence of caffeine, and the effect is greater with an increasing caffeine ratio. The interaction of aromatic phenylalanine residues of peptides with caffeine restricts the interpeptide interaction tendency. Upon increasing the number of caffeine molecules, interaction of caffeine with other hydrophobic residues also increases. Thus, the hydrophobic core-recognition motif of amyloid formation of peptides is physically blocked by caffeine, thereby abolishing the self -assembly formation.