Large basis set ab initio calculations of the dipole polarizabilities and second hyperpolarizabilities of a large set of organic molecules have been carried out and the results have been used to assess additivity and transferability of atomic contributions to the overall molecular response tensors. Reasonable estimates of the mean second hyperpolarizability response can be obtained from summing atomic parameters obtained here, though the reliability of the estimates is worse than what is found Tur dipole polarizabilities. Individual tensor elements are not as well determined from transferable, additive contributions, which means that. the orientational nature of the response is more subject to local bonding features.