The effect of flow nonuniformities existing near the distributor of a liquid fluidized bed containing very low-density particles (ρs = 1.05 g/mL) has been investigated experimentally. Immobilized enzyme or cell bioreactors operated as liquid fluidized beds often employ low-density particles as the support matrix containing the immobilized biocatalyst. With poorly designed multihole distributors, dead zones can be created which seriously undermine the performance of the bioreactor due to the lack of nutrients. Design guidelines are provided for distributors to minimize the inlet flow disturbances, and hence eliminate potential distributor region problems. As a result, the dispersion model, which is normally used for design purposes, can then be applied.