Aortic graft infection may result in high mortality ranging up to 88%. Therefore, early diagnosis is imperative in the treatment of this serious complication. Computerised tomography (CT) is considered as a sensitive tool in the diagnosis of aortic graft infection. Some findings used as the criteria for infection, such as periprosthetic gas and fluid are, however, normal postoperative findings. The aim of this prospective study was to compare CT-scan and Tc-99m-HMPAO labelled leucocytes in the early diagnosis of aortic graft infection. The present study includes 24 consecutive patients (all men, age 70 +/- 8 years, range 55-85 years), who were operated on for abdominal aortic aneurysm. Prosthetic and suture materials were the same in all operations. Each patient was examined with the aid of CT-scan and imaged with Tc-99m-HMPAO labelled leucocytes 2 weeks and 3, 6 and 12 months after the reconstructive aortic surgery. Two radiologists and two specialists in nuclear medicine examined the data independently without knowing the clinical picture of the results of any other examinations of the patients. Seven patients (7/24; 29%) showed significant accumulation of labelled leucocytes in the first imaging (2 weeks postoperatively) with Tc-99m-HMPAO labelled leucocytes. Three months after the surgery only four patients (4/24; 17%) were positive in this respect. One of these patients had clinically proven aortic graft infection and another positive was a patient with resected and reconstructed mycotic aneurysm. CT-examination in all scans was suggestive for aortic graft infection in two cases (2/24; 8%), but neither of these patients showed any signs of infection.(ABSTRACT TRUNCATED AT 250 WORDS)