Salmonellae are gram-negative bacteria that cause gastroenteritis and enteric fever. Salmonella virulence requires the coordinated expression of complex arrays of virulence factors that allow the bacterium to evade the host's immune system. All Salmonella serotypes share the ability to invade the host by inducing their own uptake into cells of the intestinal epithelium. In addition, Salmonella serotypes associated with gastroenteritis orchestrate an intestinal inflammatory and secretory response, whereas serotypes that cause enteric fever establish systemic infection through their ability to survive and replicate in mononuclear phagocytes. This review explores the molecular basis of selected Salmonella virulence strategies, with an emphasis on general themes of bacterial pathogenesis as exemplified by Salmonella.