[en] An experimental program was undertaken to extend the data on the sorption and desorption of iodine on graphite to more realistic high-temperature gas-cooled reactor (HTGR) operating conditions. This was accomplished by heating compacts of H-451 or S-2020 graphite at 250 to 1000⁰C in continuously flowing helium (at atmospheric pressure) that contained iodine at pressures of 10^-6 Pa (10^-11 to 10^-1 to 10^-6 bar). Equilibrium adsorption data were generally well-behaved and reproducible with the H-451 graphite. Type S-2020 graphite sorbed more iodine, especially in the temperature range 700 to 800⁰C. Although desorption appeared to initiate as reversible sorption, the rate of loss of iodine decreased with time. During desorption from the S-2020 graphite at 700 and 800⁰C, a temporary plateau was reached that was sensitive to helium flow and pressure