Two rotational isomers, trans and gauche, were detected for the isopropyl alcohol molecule from the analysis of the microwave spectrum. The rotational constants of the trans form were obtained A = 8488.99, B = 8041.75, and C = 4765.19 MHz for the H-species, (CH 3) 2CHOH, and A = 8098.72, B = 7917.76, and C = 4680.75 MHz for the D-species, (CH 3) 2CHOD. Rotational constants averaged for the two lowest torsional states were estimated for the normal species of the gauche form to be A = 8566.03, B = 7992.73, and C = 4714.59 MHz. Dipole moment of the trans form of the H-species obtained was μb = 1.40 ± 0.03, μc = 0.73 ± 0.02, and μt = 1.58 ± 0.03 D. The a-type lines, characteristic of the gauche form, were observed for the H-species. From a preliminary analysis of these a-type lines, the energy difference between the ground and the first excited torsional state was estimated to be ∆ = 46 GHz. The barrier height was obtained to be V3 = 1.68 kcal/mole by assuming a threefold symmetry for the internal rotation of the OH group.