Smog chamber/FTIR techniques were used to study the kinetics and mechanism of the reaction of Cl atoms with nitrobenzene (C₆H₅NO₂) in 10-700 Torr of N₂, or air, at 296 K. The reaction proceeds with a rate constant k(Cl + C₆H₅NO₂) = (9.3 ± 1.9) × 10^-13 cm³ molecule^-1 s^-1 to give C₆H₅Cl and NO₂ products in essentially 100% yield. The observed product yields suggest that the reaction proceeds via a displacement mechanism (probably addition followed by elimination). The UV-visible absorption spectrum of C₆H₅NO₂ was measured. Photolysis of C₆H₅NO₂ is estimated to occur at a rate of (3 ± 2) × 10^-5 s^-1 for a solar zenith angle of 25° (representative of a typical summer day at 40°N) and is likely to be the dominant atmospheric loss mechanism for C₆H₅NO₂.