Patients with systemic rheumatic diseases may be admitted to the ICU because of worsening of or development of a new manifestation of the rheumatic disease, infections caused by immunosuppression, or adverse effects of drugs used to treat rheumatic diseases. Sometimes an unrelated, acute disorder may become life threatening because of the underlying rheumatic disorder. Rheumatoid arthritis is the most common rheumatic disease seen in ICU patients, followed by systemic lupus erythematosus and scleroderma. These three conditions together account for up to 75% of rheumatic cases admitted to the ICU. The respiratory system is the organ system most commonly affected in the acute process, followed by the renal, gastrointestinal, and nervous systems. More than 50% of admissions result from infections, and 25% to 35% result from exacerbation of the underlying rheumatic condition. In about 20% of patients, the rheumatic disorder may be diagnosed for the first time in the ICU. An aggressive approach should be pursued to establish the diagnosis of either disease exacerbation or infection. Delay in instituting appropriate immunosuppressive or antimicrobial therapy may result in multiple organ system failure and a poor outcome. The mortality rate in patients with rheumatic disease exceeds that predicted by the APACHE II or SAPS II scores and is higher than that in nonrheumatologic ICU admissions. The mortality may exceed 50% in patients admitted for infection; the prognosis is comparatively better for patients with exacerbations of disease activity. Renal failure, coma, and acute abdomen are predictors of poor outcome. Early recognition of abdominal complications requiring surgical intervention may help reduce mortality.