Non-small cell lung cancer can be cured if the patient is medically operable and the tumor resectable. Current diagnostic strategies are aimed to detect tumor deposits that preclude resection with curative intent. However, these strategies are rather inefficient, resulting in a large number of futile invasive procedures. In the early 1990s positron emission tomography (PET) showed promising results at its introduction in the clinic, especially in oncology. A large number of accuracy studies have reported that PET is superior to conventional imaging. However, whether PET ultimately improves patient outcome should ideally be assessed by means of a randomized controlled trial. No such design has been applied to evaluate PET in oncology so far. The PLUS study was designed to compare the current strategy of conventional methods with a strategy where PET was added after completion of noninvasive techniques. Patients considered operable by the physician at this point were then randomly assigned to PET and further consequences or to standard procedures of mediastinoscopy or thoracotomy. Primary outcome events were futile thoracotomies. The trial randomized 188 patients from nine hospitals in 1 year. Patient enrollment has been stopped and data collection is in progress. The results will be published in 2001. Control Clin Trials 2001;22:89-98