The solids mixing in vibrating particle beds has been studied by examining the effect of single stationary tubes submerged in the bed. Two size ranges of glass beads with mean sieve diameters of 99 mum and 332 mum were used in the mixing experiments. It was found that considerable enhancement in both the rate of mixing and the randomness of the mixture can be attained if a stationary tube is properly installed within the vibrating particle bed. Two mixing models, a statistical model and a stirred batch reactor model, were incorporated in the data analyses of the mixing experiments. With the tube present, the stirred batch reactor model was found to agree fairly well with experiment if appropriate values were chosen for the two adjustable parameters in the model.