Warburg first reported that tumours are characterized by abnormally increased glucose metabolism accompanied by increase production of lactate. This is a basic principle underlying cancer detection by the glucose analogue 18-F-fluoro-2-deoxy-D-glucose (FDG). FDG positron emission tomography (PET) is currently used widely to examine virtually any part of the body in order to detect tumours, e.g., lung, breast, colorectal, pancreatic and head and neck cancers, malignant lymphoma and malignant melanoma. The advantage of whole-body FDG-PET in comparison with the other imaging modalities is that it allows the entire body to be surveyed seamlessly within a reasonably short period. Furthermore, the staging of most cancers can be determined. The characteristics of whole-body FDG-PET seem to satisfy the requirements for cancer screening. PET used simultaneously with conventional tests can prevent the overlooking of cancer, reduce false-positive results and assist in the interpretation of CT and MRI images. Thus, PET can play a supportive role when used with conventional screening tests. In 1994, PET was applied to cancer screening for the first time at our Imaging Center at Lake Yamanaka in Japan. Within 12 years after starting, a total of 10,292 asymptomatic individuals (6,227 men and 4,065 women; mean age, 52.2 and 52.9 years) participated in 29,090 screening sessions. As a result, malignant tumours were demonstrated in 355 of the 10,292 participants (2.61%). PET findings were true-positive in 175 of the 355 cancers (49.3%).