The rate coefficient for the quenching of N(2D) by O(3P) has been measured by using an afterglow source and resonance absorption detection for N(2D). Quenching by known concentrations of O atoms, generated by NO titration of a nitrogen discharge, was compared with the quenching by O2, N2O, and CO2, for which the rate coefficients are well known. The rate constant for N(2D) quenching by O(3P) derived in this manner is (1.8¿0.6) ¿10-12 cm3 molecule-1s-1 at 315¿K. A small increase with temperature in this rate constant relative to that for O2 was found, consistent with an activation energy of 1¿0.5 kcal/mol for N(2D)+O(3P).