Bartonella quintana is an epi- and intracellular gram-negative rod responsible for both acute and chronic clinical manifestations. We review the literature about pathogenic mechanisms of B. quintana and discuss our data. Our efforts to clarify Bartonella quintana pathogenesis run on two parallel tracks. The first one concerns interactions between Bartonella quintana and endothelial cells by evaluation and modulation of apoptosis, signal transduction pathways and inflammation. The second one concerns some biological activities of Bartonella quintana endotoxin on human whole blood and endothelium. The elucidation of the mechanisms regulating the inflammatory/proliferative pattern of chronic clinical manifestations of Bartonella quintana infections may offer a contribution for addressing the pathogenesis of intracellular bacterial persistence.