The aims of this study were (a) to estimate the prevalence of pain and eight other common symptoms in a large population of patients with advanced cancer from different palliative care centers, and (b) to assess the differences in prevalence of the symptoms by primary site. In 1990-1991, the prevalence of eight major symptoms and performance status were assessed prospectively among 1840 cancer patients in seven hospices in Europe, the United States, and Australia. The data were collected at each institution using structured data collection sheets from the World Health Organization's (WHO) Cancer and Palliative Care Unit. The prevalence of moderate to severe pain was 51%, ranging from 43% in stomach cancer to 80% in gynecological cancers. Nausea was most prevalent in gynecological (42%) and stomach (36%) cancers, and dyspnea (46%) in lung cancer. There were statistically significant differences in the prevalence of most symptoms depending on the primary site of cancer and the hospice. Population-based follow-up studies are needed to document the incidence and prevalence of symptoms throughout the course of the disease.