Infection continues to be a significant cause of morbidity and mortality in patients with rheumatic diseases, and, consequently, early diagnosis and treatment of infection is critical to the successful medical management of these patients. The intensity of immunosuppressive therapy is the dominant risk factor for infection in this patient population. Because the manifestations of infection in patients with rheumatic diseases are highly variable, the clinician must always be vigilant about the possibility of infection even if the clinical presentation is highly suggestive of an exacerbation of the underlying disease. We have stressed a systematic and individualized approach in the diagnostic evaluation of suspected infection in these patients. The first part of the evaluation involves forming a list of the most likely pathogens based on a detailed history and physical examination and the intensity and type of immunosuppressive therapy the patient is receiving. The physician must then formulate a plan designed to establish a diagnosis expeditiously and with the least morbidity.