The effects of Shiga-like toxins on the morphology and protein synthetic capability of HeLa cells in tissue culture could be prevented by brefeldin A, an inhibitor of certain intracellular Golgi functions. Brefeldin A was without effect on the binding of Shiga-like toxin to cells. These results provide evidence that the Shiga-like toxins are first processed by the Golgi before moving to their 60S ribosome target site.