Of the five promoters detected for the ftsZ gene in Corynebacterium glutamicum, three were located within the coding region of the upstream ftsQ gene and two within the intergenic ftsQ-ftsZ region. The most distant ftsZ promoter showed activity in Escherichia coli and controlled high-level transcriptional expression of ftsZ in C. glutamicum. Quantitative Western blotting showed that all five promoters were active during the exponential growth phase and down-regulated during stationary phase. This tightly controlled expression of ftsZ in C. glutamicum indicated that small changes in the amount of FtsZ protein strongly affect bacterial cell viability. The controlled overexpression of ftsZ in C. glutamicum, using the promoter of the gntK gene (PgntK), resulted in approximately 5-fold overproduction of FtsZ, an increase in cell diameter, and a highly variable localization of the protein as spirals or tangles throughout the cell. These results suggest that the intracellular concentration of FtsZ is critical for productive septum formation in C. glutamicum. Our observations provide insight into the mechanisms used by the coryneform group, which lacks actin homologs and many regulators of cell division, to control cell morphology.