  The anomalous chromomagnetic moment of the top quark arises from one loop
corrections to the vertex $\bar t t g$. We give explicit formulae for this
anomalous coupling in the framework of the standard model, the two Higgs
doublet model and the minimal supersymmetric standard model. We compare the
results for the anomalous coupling with the bound $-0.03 \leq \Delta \kappa
\leq 0.01$ emerging from the analysis of $b \to s \gamma$ process with an
on-shell bremsstrahlung gluon. This enables us to study the allowed region of
parameters of the models under consideration.
