  We study the complete one-loop contributions to the chromagnetic dipole
moment $\Delta\kappa$ of the top quark in the Standard Model, two Higgs doublet
models, topcolor assited technicolor models (TC2), 331 models and extended
models with a single extra dimension. We find that the SM predicts
$\Delta\kappa = - 0.056$ and that the predictions of the other models are also
consitent with the constraints imposed on $\Delta\kappa$ by low-energy
precision measurements.
