Ga-67 SPECT was crucial in making the diagnosis of infectious endocarditis in a 28-year-old man with a history of aortic valve replacement who was referred to the nuclear medicine service because of persistent fever. In the planar left anterior oblique view, an area of slight, diffuse activity was noted. The shape and site of the infectious focus were well defined by Ga-67 SPECT. After Ga-67 imaging, results of a computed tomographic (CT) scan were negative and the patient was treated with antibiotics and discharged from the hospital after showing clinical improvement. However, the fever returned and he was readmitted. A second Ga-67 SPECT was also positive, but a spiral CT scan showed only minor inflammatory changes. Finally, transesophageal ultrasonographic images suggested vegetation on the prosthetic valve. Cultures of the graft and the valve were obtained surgically and showed staphylococcal endocarditis. Exaggerated confidence in negative CT scan results led to unnecessarily delayed surgical treatment of the infection. Ga-67 SPECT was a powerful noninvasive tool in the diagnosis of infectious complications after prosthetic valve surgery.