We review recent theoretical and experimental work on the metal to insulator transition in doped semiconductors. The spin excitations on the insulating side of the transition can be described in terms of a spin‐ 1/2 Heisenberg antiferromagnet with the spins randomly located in space. Numerical analysis of this Hamiltonian has led to a fairly complete understanding of the static spin susceptibility and the electron spin resonance spectrum. The physics on the metallic side far from the transition is also fairly well understood in terms of a recently developed theory of the disordered Fermi liquid. The physics near the transition point is, however, still not clear. All the experimental evidence indicates the presence of local electronic moments on the metallic side of the transition. Recent theoretical work and open problems in the description of such a metallic phase are briefly discussed.