The extinction point, time-dependent flame temperature, relative [OH], and the instantaneous luminosity of a flame during the unsteady extinction process were measured in non-premixed counterflow flames, and characteristics of each parameter near the extinction limit were investigated. We found that the unsteady extinction point is much higher than the steady extinction point and OH radical is a more adequate indicator of extinction than temperature, especially for turbulent and unsteady flames. (c) 2005 The Combustion Institute. Published by Elsevier Inc. All rights reserved.