We evaluated positron emission tomography (PET) with 2-[fluorine-18]fluoro-2-deoxy-D-glucose (FDG) in the detection of recurrent head and neck cancer, and compared visual and quantitative interpretation of PET images for their accuracy in the identification of tumour recurrence. Sixty-two FDG PET studies were performed in 56 patients having a total of 81 lesions, which were clinically suspected for recurrent carcinoma of the head and neck. The PET images were interpreted visually, and tracer uptake was quantitated as the standardised uptake value adjusted to body weight (SUV). Sensitivity of visual interpretation of the PET images for the presence of malignancy ranged from 84 to 95%, and specificity from 84 to 93%, respectively, depending on the selected scheme for grading of the lesions. Malignant lesions accumulated significantly more FDG than the benign ones (the median SUVs were 6.8 and 3.3, respectively, P