BACTERIAL ARTHRITIS THAT occurred in four patients during neurosurgical convalescence is reported. Three patients had a cerebral aneurysm clipped after a subarachnoid hemorrhage, and one had herpes simplex encephalitis with a possible temporal lobe hemorrhage. All four patients had been treated with steroids. A total of six joints were infected, two patients with an infection in one joint each, and two with a metachronous infection in two joints. The interval between the onset of local symptoms and the definitive diagnosis ranged from 0 to 44 days. A delay in diagnosis severely compromises joint function, and all four of these patients were left with an associated significant musculoskeletal disability. Bacterial arthritis is well recognized in the immunocompromised patient, but, to our knowledge, has not been described in this particular clinical setting. A patient with a sustained pyrexia of unknown origin in the neurosurgical convalescent period should be suspected of having an occult musculoskeletal infection. An isotope bone scan to facilitate early diagnosis is recommended, and this, combined with specific aggressive therapy, should preserve joint function.