The importance of the iodine chemistry in the atmosphere has been demonstrated by recent observa- tions. The uptake of ethyl iodine on black carbon surface was investigated at 298 K for the first time. Degussa FW2 (an amorphous black carbon comprising medium oxides) was used as black carbon sample. Black carbon surface was found to be deactivated in reaction with C_2H_5I, and the uptake coef- ficient (γ ) was dependent on the time of exposure. The value of (2.3±0.9)×10~(-2) was determined for the initial uptake coefficient (γ0). The result suggests that the heterogeneous loss of C_2H_5I on carbonaceous aerosols may be important under the atmospheric conditions. The importance of the iodine chemistry in the atmosphere has been demonstrated by recent observa- tions. The uptake of ethyl iodine on black carbon surface was investigated at 298 K for the first time. Degussa FW2 (an amorphous black carbon comprising medium oxides) was used Black carbon surface was found to be deactivated in reaction with C_2H_5I, and the uptake coef- ficient (γ) was dependent on the time of exposure. The value of (2.3 ± 0.9) × 10 ~ (-2) was determined for the initial uptake coefficient (γ0). The result suggests that the heterogeneous loss of C_2H_5I on carbonaceous aerosols may be important under the atmospheric conditions.