The joint scalar-velocity probability density function (pdf) modelling approach is here applied to the problem of mixing and chemical reaction in a scalar mixing layer. The cases considered are of direct relevance to the modelling of turbulent combustion applications and the main objectives of the work are: (i) To assess the applicability of joint scalar-velocity pdf solution methods in the context of realistic low Damkohler number turbulent reacting flows. (ii) To investigate a multi-scalar extension of a modified binomial Langevin scalar mixing model of Valifio and Dopazo. The latter is here used in conjunction with the generalised Langevin model for velocity statistics of Haworth and Pope. The experimental data sets by Bilger et al., obtained in chemically reacting flows with Darnköhler numbers of the order unity have been used to validate the approach. The excellent agreement obtained for both conserved and reacting scalars indicates that the reaction -diffusion coupling is accurately represented by the binomial Langevin mixing model for this flow. Comparisons with linear-eddy model results or Kerstein are also presented.