The first case has recently been reported and is briefly reviewed here. Patient 1 was a 42-year-old woman with HIV infection since 1987 (Centers for Disease Control and Prevention [CDC] Classification C3). In June 2003, she was admitted to the National Institute for Infectious Diseases, Rome, from prison because of high fever and confusion. Physical examination showed a temperature of 39.5 C, abnormal mental status, and oral candidiasis, but no gastrointestinal symptoms. Her history included lack of response to highly active antiretroviral therapy (HAART), and she exhibited HIV viremia of 413,624 copies/mL, a low CD4+ cell count (5/mm3), and leukopenia (3.0 x 103/mm3). Laboratory values were altered for aminotransferases (aspartate aminotransferase, 273 U/L; alanine aminotransferase, 77 U/L), hemoglobin (7.0 g/dL), erythrocyte sedimentation rate (136 mm in the first hour), and platelet count (34 x 103/mm3). Multiple blood cultures yielded growth of Y. pseudotuberculosis. Stool cultures and test results for antibodies against Y. pseudotuberculosis were negative. Intravenous ceftriaxone therapy was started at admission, with total remission of symptoms in 4 days. No recurrence of Y. pseudotuberculosis infection was observed during a 1-year follow-up period.