To assess the clinical value of whole-body positron emission tomography (PET) with [18F]fluorodeoxyglucose (FDG) in recurrent colorectal cancer, 35 patients were studied: 15 had resectable liver metastases, one a resectable lung metastasis, eight resectable pelvic recurrence, eight a presacral mass with equivocal findings on imaging, and three increasing serum levels of carcinoembryonic antigen (CEA) without clinical or radiological signs of recurrent disease. PET affected management decisions in seven of 16 patients with metastatic disease. In one of eight patients with pelvic recurrence demonstrated by computed tomography (CT), PET detected unknown pulmonary metastases. In five of eight presacral masses with equivocal CT findings, PET was correct and unexpected distant metastases were detected in one of these patients. In two of three patients with increasing CEA levels and normal pelvic CT findings, pelvic recurrence was identified. Overall, whole-body PET affected management in 14 patients. PET is a valuable tool for staging local recurrence and metastatic disease.