Over the last three decades, a series of clinical trials have led to the use of adjuvant pelvic radiotherapy and chemotherapy in high-risk (T3-4 or N1) rectal cancer. There is a need to improve patient selection in order to identify the group most at risk for recurrent disease. The toxicity of adjuvant therapy should be factored into this consideration. The optimal sequencing of adjuvant therapy before or after surgery, the use of short- or long-course radiotherapy, and the utility of concurrent chemotherapy is currently being examined in randomized controlled trials (RCTs). The aim of this report was to review the morbidity and mortality in all RCTs of adjuvant therapy for rectal cancer.