A study of the effects of hydrodynamic turbulent shear stress on the biological responses of carrot cell cultures (Daucus carota) has been performed over a range of turbulent shear stresses. The experimental apparatus mimics turbulent conditions similar to the impeller region of a conventional stirred tank bioreactor. The apparatus was designed with the aid of simulations made using the computational fluid dynamics package CFX4. It consists of two concentric cylinders and a rotating cylindrical rod to provide turbulent mixing. The model was based on the two dimensional structure of a cylindrical wake in an annulus. The empirical shear stress agreed well with simulated values. Cell damage was found to correlate well with both the bulk energy dissipation and 'local' energy dissipation rate. The initial results suggest that significant cell damage occurs when the maximum energy dissipation is 50 W kg(-1) and the total energy dissipation is 10(4) J kg(-1). These values are slightly higher than those reported earlier(1-2).