Experimental and theoretical efforts are combined to determine a reliable value of the static dipole polarizability of I-2. The experimental estimate of the mean dipole polarizability is alpha = 69.7 +/- 1.8e(2)a(0)(2)E(h)(-1). The polarizability of the iodine atom has also been deduced from experimental measurements and is estimated at 32.9 +/- 1.3e(2)a(0)(2)E(h)(-1). Accurate ab initio calculations predict alpha = 70.9 +/- 1.4e(2)a(0)(2)E(h)(-1) and for the anisotropy Delta alpha = 41.2 +/- 0.8e(2)a(0)(2)E(h)(-1). The deformation of the iodine molecule in the presence of general static fields has been studied and analyzed.