One of the most difficult ethical dilemmas facing health care professionals working in oncology is whether, when, how and how much to tell terminal cancer patients about their diagnosis and prognosis. The aim of this article is to review the trends in this issue worldwide. While a majority of physicians in both developed and developing countries tell the truth more often today than in the past, the assumption that truth-telling is always beneficial to patients can be questioned. The issue of truth-telling is still approached differently in different countries and cultures and there is a need for an increased awareness of cultural differences to truth-telling among patients from ethnic minorities.