With improved surgical techniques and preoperative radiotherapy (RT) the local recurrence rate in rectal cancer patients has been reduced, however the mortality rate is still high and there is a huge variation in the response to preoperative RT in patients with the same tumour stage. To improve patient's survival, it is of great importance to identify good prognostic and predictive factors that help us to select the best suited patients for preoperative RT in the future. In this thesis, we wanted to investigate the biological factors, survivin and PINCH, and the histological factors, inflammatory infiltration, fibrosis, necrosis, mucinous content, angiogenesis and lymphangiogenesis. Further we wanted to investigate these biological and histological factors in relation to preoperative RT and to clinical variables in rectal cancer patients participating in a clinical trial of preoperative RT.