Mean dipole moment derivatives determined from gas-phase infrared fundamental intensity data for 30 molecules are compared with Generalized Atomic Polar Tensor (GAPT) charges calculated from wave functions obtained with 6-31G(d,p) and 6-311++G(3d,3p) basis sets at the Hartree-Fock, B3LYP density functional, and MP2 electron correlation levels. With very few exceptions, the MP2 results are in better agreement with the experimental values than are the B3LYP results calculated with the same basis set, although the differences between these calculated results are often small. The Hartree-Fock results deviate most from the experimental values. For all atoms studied here, C, H, F, Cl, N, O, and S, the MP2/6-311++G(3d,3p) results agree most closely with the experimental values with rms errors of 0.059, 0.013, 0.044, 0.045, 0.030, 0.041, and 0.014E respectively. Although the calculated results for charges between -0.5 and +0.5e seem to deviate randomly from the experimental results, calculated charges ranging from +0.5 to +2.0e tend to be slightly larger than the experimental values. This is a consequence of the fact that the MP2/6-311++G(3d,3p) calculations tend to overestimate infrared intensity sums for molecules with more polar bonds and intensity sums above 500 km mol(-1). The results reported here show that the calculated charge values seem to be converging to the experimental values as the basis set becomes more extensive, 6-31G(d,p) to 6-311++G(3d,3p), and as the electron correlation level becomes more complex, Hartree-Fock to B3LYP density functional to MP3. Experimental mean dipole moment derivative values are shown to be consistent with trends in atomic charge values expected from chemical arguments for the halomethanes, hydrocarbons and Group IV hydrides.