The structural properties and thermochemistry of the UFn and UCln (n=1,...,6) molecules have been investigated using hybrid density functional theory and a small-core (60 electrons) relativistic effective core potential for the uranium atom. For the first time Bond dissociation energies for this whole series are computed and shown to be in good agreement with experiment. The geometry and electronic structure of each molecule was characterized. (C) 2004 American Institute of Physics.