The conformation of thymosin beta 9 in solution of 40% (v/v) 1,1,1,3,3,3-hexafluoro-2-propanol-d2 in water has been investigated by two-dimensional 1H-nmr spectroscopy. Under this condition thymosin beta 9 adopts an ordered structure. The determination of the conformation of the peptide was based on a set of 304 approximate interproton distance constraints derived from nuclear Overhauser enhancement measurements. The conformation of thymosin beta 9 includes two helical regions from residues 4 to 27 and 32 to 41. The two helices are separated by a poorly defined loop region between amino acids 28 and 31; the N-terminus of thymosin beta 9 shows random-coil structure only.