The deposition of iodine on low chromium-alloy steel (1% Cr—1/4% Mo alloy) has been investigated in vacuo at 316, 400, and 482°C using a pseudoisopiestic (static) method. An adsorption isotherm was obtained at 400°C over an iodine (monotomic) pressure range of 2.9 × 10-9 to 5.1 × 10-7 atm. The levels of iodine deposition at 400°C ranged from 3.8 to 23.2 µg I/cm2; these values are in agreement with data obtained using transpiration techniques. The low-level sorption data are interpreted on the basis of the dissociation of I2 to yield monatomic iodine as well as the interaction with the steel surface to form volatile iron iodides, which were deposited in cooler regions of the apparatus. The high-level sorption behavior of iodine on steel is in accord with the expected behavior based on the thermodynamic properties of FeI2(s).