Absolute rate constants for the reaction of O(3P) atoms with CH3NH2, C2H5NH2, (CH3)2NH, and (CH3)3N have been determined over the temperature range 298–440 °K using a flash photolysis–NO2 chemiluminescence technique. The Arrhenius expressions obtained were k2[CH3NH2] =9.02×10−12 exp[−(1650±200)/RT] cm3 molecule−1 sec−1, k2[C2H5NH2]=1.13×10−11 exp[−(1275 ±200)/RT] cm3 molecule−1 sec−1, k2[(CH3)2NH]=1.52×10−11 exp[−(550±200)/RT] cm3 molecule−1 sec−1, k2[(CH3)3N] =1.08×10−11 exp[(415±200)/RT] cm3 molecule−1 sec−1, with room temperature rate constants of (5.65±0.57) ×10−13 cm3 molecule−1 sec−1, (1.33±0.14) ×10−12 cm3 molecule−1 sec−1, (6.12±0.62) ×10−12 cm3 molecule−1 sec−1, and (2.20±0.22) ×10−11 cm3 molecule−1 sec−1, for CH3NH2, C2H5NH2, (CH3)2NH, and (CH3)3N, respectively. Possible reaction mechanisms are discussed.