This paper describes a study of the formation and destruction of NO in turbulent propane diffusion flames with recourse to both experiments and modelling. Detailed in-flame measurements of local mean gas species concentrations of O-2, CO, CO2, unburnt hydrocarbons and NO, and local mean gas temperature have been performed for three flames - two of them with the same Froude number and two with the same Reynolds number. These experimental data have been analysed with the aid of a mathematical model. For the NO calculations, three reaction schemes have been used: the Zeldovich reactions, an overall approximate prompt reaction, and a 27 reaction scheme, which includes the thermal NO and the prompt NO reactions and the NO to HCN recycle via fuel NO reactions. The main conclusions are that in the present flames: (I) the prompt NO (or Fenimore) mechanism is the dominant route for the NO formation; and (2) the reactions between NO and hydrocarbon radicals, recycling NO to HCN via the fuel NO reactions, play an important role in the global NO reduction.