In Spain, there is a general tendency to conceal the prognosis from a terminally ill patient. We conducted grounded-theory-based, phenomenological, qualitative research on this using a final sample of 42 in-depth interviews with doctors and nurses from different fields. We found that most health professionals believe that although patients don't ask questions, they know what is happening to them. Many professionals feel bad when communicating bad news. In hospitals, doctors take responsibility for doing so. The attitudes of professionals are influenced by their sense of responsibility and commitment to the principle of patient autonomy, as well as to the level of their agreement with the cultural context. The tacit agreement of silence makes communication impossible: the patient does not ask questions, the health professional does not want to be interrogated, and family members don't talk about the disease and want health professionals to follow their example. This situation is detrimental to patients and their families and leads to suffering, low levels of satisfaction, and feelings of guilt and helplessness. Health care professionals must acquire the means and the skills for communicating bad news.