The atmospheric chemistry of pyruvonitrile, CH3C(O)CN, was studied experimentally using FTIR smog chamber techniques. All experiments were performed at 296 +/- 2 K and 700 Torr. The rate constants k (CH3C(O)CN + Cl) = (1.01 +/- 0.26) x 10 (-14) cm(3) molecule(-1) s(-1) and k(CH3C(O)CN + OH) = (3.02 +/- 1.11) x 10(-13) cm(3) molecule(-1) s(-1) were determined using the relative rate method. NCC(O)OONO2, ClC(O)OONO2, CO and HCN were identified as products from the atmospheric degradation of CH3C(O)CN. The atmospheric lifetime of CH3C(O)CN was calculated to 38 days and GWP(100) to 1.