This Letter reports on the first direct measurement of N-2 (C(3)Pi(u), v = 2) electronic quenching rate constant by optical-optical double resonance laser-induced fluorescence. The value found, (4.19 +/- 0.13)x 10(-11) cm(-3) s(-1), solves the discrepancies between the literature data. The technique opens the way to a complete and definitive investigation of electronic quenching and V-V relaxation in the whole C(3)Pi(u) state vibrational manifold by means of a minimal laser configuration. (c) 2005 Elsevier B.V. All rights reserved.