The conformational properties of peptides 1–8, 10 and 11 of b³-aminoxy acids with different side chains on the b-carbon were investigated by using NMR, IR, CD spectroscopy and X-ray crystallography. b N-O turns and b N-O helices, involving a nine-membered-ring intramolecular hydrogen bond between NH_i+2 and CO_i, were formed in b ³-aminoxy peptides. X-ray structures of diamides 3, 5 and 7 revealed that in the b N-O turns, the N-O bond could be anti or gauche to the C_a-C_b bond depending on the size of the side chain. While parallel strand structures were also found in solid state for diamide 1 and triamide 10, turn and helix were the predominant conformation in non-polar solvents, respectively.