Disclosure of a diagnosis of cancer to patients is a major problem among physicians in Korea. Many questions arise when considering issues involved in telling the diagnosis of cancer beyond the question of whether to tell. But there has been no consensus guideline on how, and in what context, to tell the diagnosis of cancer to the patients. The review of the literature reveals that the attitudes of physicians on the truth telling have been changing from favoring non-disclosure to disclosure over time. The disclosure rate was 81.8% in a Korean survey performed in 1990, while it was 65% in a survey in 1979. The younger the patient's age was, the higher the disclosure rate was. This tendency was same in Korean nurses and patients. The majority of Korean patients wanted their doctors to break the bad news, not only because the patients wanted to obtain detailed information about their conditions but also because they believed their doctors. They also wanted their family to hear the truth first, immediately after the diagnosis had been confirmed. The most important issue in the process of disclosing a diagnosis of cancer to patients is truth. Otherwise, doctors will lose the chance to give help to the patients when they are in real need of doctor's help at the very end of their lives.