The conformation of 1-butanol has been studied in the solid, glassy, liquid, and matrix-isolated states and in aqueous solution by the combined use of vibrational spectroscopy and ab initio molecular orbital calculations. The molecules in the solid state adopt two conformations of TTt and TTg for the bond axes of CH3CH2-CH2-CH2-OH; T or t represents trans, and G or g represents gauche. In the liquid and glassy states, the molecules take diverse conformations of TTx, TGx, GGx, and GTx, where x represents any of t, g, and g’. The experimental finding that the TTx and TGx forms are more stable than the GGx and GTx forms in these phases is consistent with the results of ab initio calculations. The similarity in the conformational stability between the trans and gauche conformations for the C-C bond adjoining the C-OH bond is evidenced by spectral observations and ab initio calculations. The gauche conformation about the CC-CO axis is stabilized by the van der Waals interaction between the hydroxyl oxygen and the hydrogen of the C, position. In an argon matrix, 1-butanol molecules exist as monomer, dimer, and polymer species, and the dominant conformations present are TTx and TGx. The annealing process causes the molecular aggregation, which takes place at the hydroxyl part of the molecules. In aqueous solution, the GTx and/or GGx form is more populated than in the neat liquid. This conformational behavior is explained by favorable incorporation of 1-butanol molecules with bent structure into the lattice of the water structure.