Several subgrid-scale (SGS) scalar flux (tau(iA)) and unmixedness (lambda(AB)) models are presented for large eddy simulation (LES) of heat and mass transport in turbulent flows. The models are similar to those considered in [Int. J. Heat Mass Transfer, in press] for SGS stresses and are based on the information residing at filtered or resolved field. All closures are implemented "locally" and are assessed a priori and a posteriori via data generated by direct numerical simulations of several nonreacting and reacting turbulent flows. A priori assessment indicates that the local values of tau(iA) and lambda(AB), obtained by new "serial decomposition" closures are closer to "true" values than those obtained by dynamic-diffusivity and two-parameter mixed models. A posteriori assessment also indicates that the statistics of the scalar field in nonreacting and reacting flows are better predicted by LES when new SGS models are used. (C) 2003 Elsevier Science Ltd. All rights reserved.