A consistent method to derive the parameterized NO source term from a given flamelet library is presented. The approach was tested by conducting PDF simulations and comparing computed solutions of the Sandia D flame with measurements. The parameterization is based on laminar flamelets with additional parameters for NO formation and radiation. To obtain feedback of the NO concentration on the NO source term, evolution to equilibrium is calculated with a complex chemical mechanism (including nitrogen chemistry), whereas the concentration of all non-nitrogen species are parameters obtained from flamelet profiles. With this method, which requires an appropriate initialization of the nitrogen containing species, unrealistically large NO source terms are avoided, which is a shortcoming of previously devised methods. In addition, to properly account for radiative heat losses, an additional progress variable was introduced. Simulation results obtained with our PDF method are in excellent agreement with experimental data. While the NO concentration values appear too high (by approximately 30% at the exit of the burner), if radiation effects are ignored, their match is very good, if radiation effects are taken into account. (C) 2010 The Combustion Institute. Published by Elsevier Inc. All rights reserved.