Coxiella burnetii established a persistent infection of various cell lines including L929 mouse fibroblasts. Although the basis for such persistence is unknown, the phenomenon does require continual growth, proliferation, and maintenance of viability of the host cells. We examined the effect of short- and long-term infection on the host cell's generation time and cell cycle. Flow cytometric studies of actively growing normal and infected cells stained with mithramycin or propidium iodide revealed no significant difference in cell cycle distribution patterns or changes in ploidy level associated with persistent infection with either phase I or phase II C. burnetii. The population doubling times of infected and normal cells were similar.