Epidemiological studies have shown an inverse relationship between nut consumptionand chronic diseases of humans. For this reason, commercially-viable U.S. cultivars wereassessed for their antioxidant and anti-inflammatory constituents. Acetonic extracts of defatted pecans possessed marked in vitro antioxidant capacities as determined by a number of assays including total phenolics content (TPC), ferric reducing antioxidant potential (FRAP),hydrophilic-oxygen radical absorbance capacity (H-ORACFL), and total procyanidins content (DMAC). Depending on the cultivar, H-ORACFL values ranged from 13.5 3.5 to 25.5 3.0 mmol Trolox eq/100 g. The procyanidins content of crude extracts (420 20 to 655 43 mgprocyanidin B2 eq/100 g) correlated better with H-ORACFL data than TPC values. The impact of roasting on the antioxidant activity and phenolics content was investigated. Pecans were roasted in an impingement oven at 175C for 8.2 min. No significant differences were observed in FRAP quantities and only one cultivar showed a significant decrease in H-ORACFL. Significant decreases were observed for both TP (~10%) and PAC (~25%) contents. Fractionation of the crude acetonic extracts by Sephadex LH-20 column chromatography into low-molecular-weight (LMW) and tannin-rich phenolic compounds (HMW) was achieved. Results indicated that the tannin-rich fraction, comprised of proanthocyanidins, possessed substantially more antioxidant activity than the LMW phenolic fraction. Phenolic acids identified in the crude acetonic extract and LMW phenolic fraction by RP-18 HPLC included gallic, ellagic, protocatachuic, and p-hydroxybenzoic acids as well as the proanthocyanidin monomers,catechin; these were tentatively identified, confirmed using ESI-LC-MS and quantified (both in their free, esterified, and bound forms) by HPLC. Normal phase-HPLC revealed that the tannin rich fraction, which accounted for most of the antioxidant activity, comprised both hydrolyzable and condensed tannins. Degrees of polymerization for the tannin-rich samples were determined to contain monomers-pentamers with dimers representing the largest fraction (56.7%). Anti-inflammatory properties of the crude and acetonic extracts (both LMW and HMW fractions) were evaluated using lipopolysachharide-stimulated RAW 264.7 macrophage cells. Nitric oxide, an index of inflammation, was measured using the GRIESS assay. The LMW fraction proved to be most effective and showed a dose-dependent effect.