NMR and CD spectroscopy have been used to examine the conformation of the peptide, beta(12-28), (VHHQKLVFFAEDVGSNK) in aqueous and 60% TFE / 40% H2O solution at pH 2.4. In 60% TFE solution, the peptide is helical as confirmed by the CD spectrum and by the pattern of the NOE cross peaks detected in the NOESY spectrum of the peptide. In aqueous solution, the peptide adopts a more extended and flexible conformation. Broadening of resonances at low temperature, temperature-dependent changes in the chemical shifts of several of the CH alpha resonances and the observation of a number of NOE contacts between the hydrophobic side-chain protons of the peptide are indicative of aggregation in aqueous solution. The behavior of beta(12-28) in 60% TFE and in aqueous solution are consistent with the overall conformation and aggregation behavior reported for the larger peptide fragment, beta(1-28) and the parent beta-amyloid peptide.