Rickettsial diseases continue to confound physicians because of their usually sporadic occurrence and nonspecific clinical presentation. In past years, diagnosis was confirmed only during convalescence; however, newer, more widely available methods, such as antigen detection and improved in vitro cultivation, have enabled a diagnosis at a time when therapeutic decisions are made. Molecular nucleic acid-based techniques have also expanded the spectrum of etiologic agents and illnesses caused by rickettsiae.