Adsorption of styrene on activated carbon was investigated on the basis of the adsorption isotherm, isosteric heat of adsorption, and compressed volume of condensed styrene. Regeneration of spent activated carbon was examined by the extraction of styrene with organic solvents. The Langmuir equation could be applied to the adsorption isotherms of styrene on activated carbon. The isosteric heats of adsorption of styrene on activated carbon Nos. 1-3 and 5-were less than twice the value of the heat of condensation of styrene (ΔH₀=9.64 kcal/mol) in the range of θ 0.2 to 1.0, and therefore, styrene adsorbed in this range of θ seemed to be physisorbed on activated carbon. Styrene physisorbed on activated carbon seemed to be compressed in the pores. Spent activated carbon could be regenerated by extracting the styrene with acetone at about 30° and its adsorptive capacity became approximately equal to that of fresh activated carbon.