Sinusitis occurs in a wide range of immunocompromised hosts, including neutropenic patients, diabetic patients, patients in critical care units, and patients with HIV infection. Reversal of underlying risk factors, such as neutropenia or diabetic ketoacidosis, is essential in the treatment of fungal rhinosinusitis. Aggressive surveillance, high clinical suspicion, and early diagnosis and treatment are all critical aspects of sinusitis management. Sinusitis is increasingly recognized as the cause of occult cases of fever in critical care patients. Sinusitis in HIV-infected patients becomes more prevalent as immunosuppression worsens.