  We present a theory of the metal-insulator transition in a disordered
two-dimensional electron gas. A quantum critical point, separating the metallic
phase which is stabilized by electronic interactions, from the insulating phase
where disorder prevails over the electronic interactions, has been identified.
The existence of the quantum critical point leads to a divergence in the
density of states of the underlying collective modes at the transition, causing
the thermodynamic properties to behave critically as the transition is
approached. We show that the interplay of electron-electron interactions and
disorder can explain the observed transport properties and the anomalous
enhancement of the spin susceptibility near the metal-insulator transition.
