This survey of the current state of the art in computational models for turbulent reacting flows carefully analyzes the strengths and weaknesses of the various techniques described. Rodney Fox focuses on the formulation of practical models as opposed to numerical issues arising from their solution. He develops a theoretical framework based on the one-point, one-time joint probability density function (PDF). The study reveals that all commonly employed models for turbulent reacting flows can be formulated in terms of the joint PDF of the chemical species and enthalpy.