Caveolin-1 is a main structural component of caveolae and essential for the invagination of caveolae by forming a hairpin-shaped structure in the membrane-inserting domain (residues, 102-122). In this article, we determined the tertiary structures of the peptides comprising residues 93-126 and 101-126 of caveolin-1 in 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) aqueous solution and sodium dodecyl sulfate (SDS) micelles, respectively, by nuclear magnetic resonance (NMR) study. The self-association of the peptides in SDS and dodecylphosphocholine (DPC) micelles was also studied by circular dichroism (CD), NMR, and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) techniques. Our results indicated that both peptides form a helix-break-helix structure with two helices spanning over Leu103-Phe107 and Ile117-His126 and a loop ranging over Gly108-Gly116. The longer peptide 93-126 showed a stronger propensity to aggregate than the shorter peptide 101-126 in the micelles. Our results suggested that the glycine residues at positions 108 and 116 are important for the break of the helical structure of the membrane-inserting domain and the segment Thr93-Arg101 flanking the membrane-inserting domain may play a role in the self-association of the caveolin-1 protein at cellular membrane.