The accuracy of density functional theory in the description of geometries and atomization energies has been assessed by comparison to experimental data for a series of first-row closed-shell molecules. Six commonly used functionals (B3LYP, B3PW91, B3P86, BLYP, BPW91, BP86) were investigated in combination with the correlation-consistent basis sets [cc-pVxZ and aug-cc-pVxZ where x=D(2), T(3), Q(4), 5]. The convergence of molecular properties with respect to increasing basis set size has been examined. A full statistical error analysis has been performed, assessing the success of each functional with respect to each basis set in terms of both accuracy and precision. Overall, there is smooth convergence towards the Kohn-Sham limit for the hybrid functionals B3LYP and B3PW91, whereas the nonlocal functionals are relatively insensitive to basis set choice. (C) 2004 American Institute of Physics.