Through an enormous research effort over the past five decades and especially due to early screening, an increasing number of cancers are potentially curable. Patients expand immeasurable energy in adhering to treatment plans and supportive care. Unfortunately, nothing prepares them for the anxiety that often comes with completion of therapy. More importantly, physicians are not properly equipped with data from controlled trials to define appropriate post-treatment surveillance, data with which they could educate patients and allay their fears. The goal of post-treatment surveillance is to enable the early detection of relapses and thus enhance the possibility of subsequent cure. Accordingly special follow-up is appropriate only for patients who can receive a second-line therapy. Clinical trials support conservative, rather than aggressive, surveillance to detect curable local relapse of breast tumors and potentially surgically curable metastases (mainly in the liver) of colon cancer. For germ-cell tumors, second-line treatments are potentially curative in nearly all instances. Follow-up for other cancers depends on patients' anxiety levels and on the costs of surveillance.