An extension of the Kronig–Penney model to treat mixings of different valleys in superlattices is presented. The value of the mixing parameter &agr; used in the model is deduced by comparison with more sophisticated theory and various experiments for the GaAs/AlAs material system. It is shown that with the use of a single value for the mixing parameter, this simple and efficient model can reasonably reproduce the important aspects of valley mixing effects in GaAs/AlAs superlattices over a wide range of layer thicknesses.