The concept of using the upper stirrer for foam disruption in a bioreactor agitated by multiple impellers has recently been published by Hoek, et al. (1997). This concept, stirring as foam disruption (SAFD), was shown by them to be effective with a range of impellers. However, the commonly used (so-called) standard Rushton turbine of one-third the fermenter diameter was not included. This paper fills that important gap. By measuring the foam height, the holdup, the power draw and the velocities of the liquid in the dispersion just below its top surface, it is concluded that the SAFD concept does not work well with the standard Rushton turbine. This is because the amount of broth for which foam can be disrupted is less than that found with all the other impellers tested to date; and even when foam disruption occurs, significant flow instabilities and torque fluctuations are found. Perhaps the poor performance of this impeller, which has been used so frequently in industry and in academic studies, explains why the concept of SAFD was not developed earlier.