Aggregation of soluble, monomeric beta- amyloid (Abeta) to oligomeric and then insoluble fibrillar Abeta is a key pathogenic feature in development of Alzheimer's disease (AD). Increasing evidence suggests that toxicity is linked to diffusible Abeta oligomers, rather than to insoluble fibrils. The use of naturally occurring small molecules for inhibition of Abeta aggregation has recently attracted significant interest for development of effective therapeutic strategies against the disease. A natural polyphenolic flavone, Kaempferol-3-O-rhamnoside (K-3-rh), was utilized to investigate its effects on aggregation and cytotoxic effects of Abeta42 peptide. Several biochemical techniques were used to determine the conformational changes and cytotoxic effect of the peptide in the presence and absence of K-3-rh.