Velocity field and CH distribution are measured simultaneously using particle-image velocimetry (PIV) and planar laser-induced fluorescence (PLIF) of CH in piloted, turbulent, jet flames in coflow. The CH distribution is found to correspond well with the location of the stoichiometric velocity, U-s both instantaneously and on average. In addition, the CH distribution is observed to align with high-strain rate regions; however, significantly higher values of the maximum strain rates, compared to the mean value, are frequently observed. The residence time in the flame surface as represented by CH, tau(f) remains nearly constant with axial distance downstream and is found to scale as T, similar to d/U-b, where d and U, are nozzle exit diameter and bulk nozzle-exit velocity, respectively. The mean value of the compressive principal strain rate is observed to decrease along the axial direction and shows a good correlation to a S similar to (x/d)-(0.7) relation for a wide range of jet Reynolds numbers. Finally, the two-dimensional dilatation is not seen to be a good marker of the flame position, unlike the case for premixed flames. (C) 2003 The Combustion Institute. All rights reserved.