High-resolution infrared spectra of the symmetric top isobutane CH(CH3)(3) were assigned with the help of ab initio calculations. The strong parallel band nu(5)(a(1)) with an origin at 1396.54741(76) cm(-1) and the nu(4)(a(1)) mode, the CH2 scissors, at 1478.20363(41) cm(-1) were rotationally analyzed. The bands in the C-H stretching region were assigned with the help of an anharmonic calculation and a local mode analysis.