Adjuvant chemotherapy has led to improvements in relapse-free and overall survival in patients with breast, colon, and non–small-cell lung cancer, yet many older patients are not offered these potentially life-saving treatments. Moreover, older patients have been either excluded or under-represented in most adjuvant trials, limiting the generalizability of these treatments to older populations. Limited data in elders suggest that older patients derive significant benefits from adjuvant therapies provided they have life expectancies exceeding 5 years. Making treatment decisions in elders is challenging. Many have major comorbidities that may substantially limit life expectancy and minimize or negate the benefits of adjuvant chemotherapy. In this review, we discuss the potential benefits of adjuvant treatment in older patients with solid tumors with a focus on general principles involved in the selection of adjuvant therapy for patients with breast, colon, and non–small-cell lung cancer. In addition, we discuss the role of comorbidity and how it factors in treatment decisions. Finally, we discuss future research directions and funding for elders with cancer.