Background: Due to demographic changes, the number of elderly people with cancer will increase in the next decades. In the past, elderly patients with cancer were often excluded from clinical trials. Chronological age has been considered a risk factor for increased toxicity and reduced tolerance to chemotherapy. Methods: We present a review on toxicity of chemotherapy and factors associated with toxicity in elderly patients with cancer, and we discuss chemotherapeutic agents and treatment options in treating this patient population. Results: Age is a risk factor for increased toxicity to chemotherapy and decreased tolerance. However, few trials have been reported with adjustment for age-associated changes such as impairment of functional status and increased comorbidity, which also show an independent association with increased toxicity. Published data may include several biases, such as referral and publication bias. Conclusions: Decision making in elderly cancer patients should be based on the results of a geriatric assessment. Patients with few or no limitations should be treated as younger patients are treated. Data with a high level of evidence are unavailable for patients showing moderate or severe limitations in a geriatric assessment.