The results of thermography and computed tomography of 168 patients following rectum extirpation for cancer were analysed. Of them 116 had symptoms of cancer recurrence and 52 with a poor prognosis were without signs of recurrence. In the 1st group thermography made it possible to record recurrences in 106 (91.4%) patients whereas computed tomography in 102 (87.9%). In thermography overdiagnosis was observed in 8 (6.9%) cases as a result of chronic inflammatory processes in the small pelvis. In computed tomography erroneous results were obtained in 4 (3.5%) cases. In the absence of recurrence symptoms the use of both methods made it possible to detect tumor recurrences in 11 (21.2%) patients at a preclinical stage. In the authors' opinion, thermography provides an opportunity to assume the presence of a recurring tumor and to make up a high risk group of patients who are in need of an active follow-up and thorough examination using other methods.