The work contained within this thesis focuses on the optical spectroscopic characterization and thermodynamic analysis of selected model β-sheet peptides, both two-stranded antiparallel β hairpins and three-stranded antiparallel β-sheets. Such small peptide systems that have the ability to fold in aqueous solution are invaluable toward understanding β-sheet folding and stability. Selected model peptides were utilized to examine the dependence of turn conformation and strand length on β-sheet formation. Results from FTIR and ECD spectroscopies show that the turn sequence, D Pro-Gly, is better for β-hairpin formation over Asn-Gly. Furthermore, lengthening the β-strands with Thr, which has a high propensity for β-sheet structure did not increase β-sheet content. Thermal denaturation experiments revealed broad unfolding transitions. These transitions could be fit by a two-state model approximation and independently by a statistical mechanical model, which also indicated a two-state system. The next study involved the estimated quantitation of β-sheet structure and the thermodynamic characterization of two three-stranded β-sheet models previously reported by NMR to be highly folded. We found the first model, Betanova, to be mostly unstructured by ECD and FTIR spectra analysis, and the second model, D P D P, to have a substantial amount of β-sheet structure. Their thermal denaturation profiles displayed nearly linear responses in ECD, FTIR, and fluorescence measurements. Additionally, FRET end labels attached to these peptides confirmed that D P D P is structured in solution providing substantial resonant energy transfer efficiency indicative of the proximity of the N and C termini. Betanova displayed very minor FRET efficiency. FRET efficiency for D P D P as a function of temperature or chemical denaturant concentration was virtually invariant and this was suggestive of a collapsed state for this peptide throughout the unfolding conditions spanned. Finally, a spectroscopic characterization of the structure and thermodynamic stability of a three-stranded β-sheet module, the W W domain from hYAP, was conducted. By both ECD and FTIR we determined a β-sheet content in almost perfect agreement with that obtained from the NMR solution structure. An assessment of the unfolding of this domain revealed that it behaves as a two-state cooperative system for both hydrophobic and interstrand hydrogen bonding interactions. Analysis of truncated constructs of the WW domain indicated that correct folding might require the tertiary context provided by the long (∼10 residues) and unstructured N and C terminal regions.