Colorectal cancer is a disease of the elderly, with 70% of patients being aged 65 years or older. In Western countries, the total number of elderly patients with this disease is expected to further increase in the future. Since the incidence of adverse physical or socioeconomic conditions in the elderly is higher than in younger patients, a thorough assessment of the patient's suitability for therapy should be performed before a decision is made. Using a Comprehensive Geriatric Assessment (CGA) to subdivide the population of elderly cancer patients into three groups can help to guide treatment decisions. Both in the adjuvant and in the palliative setting, there are sufficient data supporting the use of fluorouracil-based chemotherapy in fit elderly patients who can tolerate cytotoxic treatment. Systemic chemotherapy has been shown to effectively reduce mortality in the adjuvant situation and to be of clinical benefit for patients with metastatic disease in terms of longer survival, control of symptoms and quality of life. In recent years, new substances such as oxaliplatin or irinotecan have shown significant activity in the treatment of patients with metastatic colorectal cancer. However, information on how to guide the use of these new drugs in elderly patients is still lacking. Limited data from clinical trials indicate treatment efficacy in selected elderly patients comparable to that observed in younger patients, with overall manageable toxicity. Clearly, further clinical trials in elderly patients with colorectal cancer are necessary as well as the incorporation of aspects of geriatric medicine into the teaching programme of medical oncologists.