Consistent evidence supports an association between consumption of fruits and vegetables rich in polyphenolics with decreased incidence of certain cancers. Acai, a palm fruit native to South America, was previously determined to contain a diversity of polyphenolics with high antioxidant capacity, yet its bioactive properties have not been investigated. The effects of acai polyphenolics (0-250 µM) on the antiproliferation and induction of apoptosis in HL-60 human leukemia cells was investigated. Specific interactions between anthocyanins and polyphenolics in both glycosidic and aglycone forms were investigated to determine additive or synergistic responses. Polyphenolics and anthocyanins were isolated in a series of partitions using reverse phase C₁₈-columns. Ethyl acetate was used to isolate phenolic acids and flavonoids, followed by methanol to remove anthocyanins. Studied fractions included whole fruit, C₁₈-retained total polyphenolics, isolated anthocyanins, and isolated phenolic acids. Aglycones were formed following acid hydrolysis (2N HCl, 60 min at 90°ÆC). Individual polyphenolics were then characterized and quantified by HPLC-PDAD. Cell proliferation and the induction of apoptosis were determined by the MTT-colorimetric and the caspase-3 activity assays, respectively.Predominant polyphenolics in acai included cyanidin, ferulic acid, epicatechin, p-hydroxy benzoic acid (1040, 212, 129, 80.5mg/L, respectively). Catechin, gallic, protocatechuic, and free ellagic acid were also identified (ca. 60mg/L). Polyphenolic fractions at 250 µM were found to reduce cell proliferation up to 86%, and were similar among the isolates except for the isolated polyphenolics (<58%). Polyphenolic and anthocyanin fractions were non-additive in their contribution to the cell anti-proliferation activity with respect to the C₁₈-retained total polyphenolic isolate. At equimolar concentrations, the glycosidic forms induced a higher magnitude of change in vital cell parameters (proliferation and apoptosis) than their respective aglycone forms. This study demonstrated that acai offers a rich source of bioactive polyphenolics with apoptotic activity that also reduced cell proliferation in a model system for cancer.