Treatment with 20 microM brefeldin A (BFA) for 60 min caused the disassembly of the Golgi apparatus in tobacco BY-2 cells, and the effect of BFA was reversible. Connections between Golgi cisternae and the ER were observed in cells that had been treated for 15 min with BFA. BFA applied to cells at metaphase allowed the cells to form aniline blue-positive cell plates but not to complete cytokinesis. BFA seems to inhibit cytokinesis by shutting off the supply of cell-plate materials by disassembling the Golgi apparatus.