A rotating bioreactor for the cell/tissue culture should be operated to obtain sufficient nutrient transfer and avoid damage to the culture materials. Thus, the objective of the present study is to determine the appropriate suspension conditions for the bead/cell distribution and evaluate oxygen transport in the rotating wall vessel (RWV) bioreactor. A numerical analysis of the RWV bioreactor is conducted by incorporating the Eulerian-Eulerian multiphase and oxygen transport equations. The bead size and rotating speed are the control variables in the calculations. The present results show that the rotating speed for appropriate Suspensions needs to be increased as the size of the bead/cell increases: 10 rpm for 200 mu m; 12 rpm for 300 mu m; 14 rpm for 400 mu m; 18 rpm for 600 mu m. As the rotating speed and the bead size increase from 10 rpm/200 mu m to 18 rpm/600 mu m, the mean oxygen concentration in the 80% midzone of the vessel is increased by similar to 85% after 1-h rotation due to the high convective flow for 18 rpm/600 mu m case as compared to 10 rpm/200 pm case. The present results may serve as criteria to set the operating parameters for a RWV bioreactor, such as the size of beads and the rotating speed, according to the growth of cell aggregates. In addition, it might provide a design parameter for an advanced suspension bioreactor for 3-D engineered cell and tissue cultures.