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 N-2, or air, at 296 K. The reaction-proceeds with a rate constant k(Cl + C6H5NO2) = (9.3 +/- 1.9) x 10(-13) cm(3) 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) x 10(-5) s(-1) for a solar zenith angle of 25 degrees (representative of a typical summer day at 40 degreesN) and is likely to be the dominant atmospheric loss mechanism for C6H5NO2.