Cross-cultural quality of life measurement and psychosocial assessment in oncology have become reality with the translation and international validation of quality of life questionnaires. The Functional Assessment of Chronic Illness Therapy (FACIT) Measurement System, under development since 1987, produced its 4th version in November 1997. The FACIT system includes the Functional Assessment of Cancer Therapy (FACT), the Functional Assessment of Human Immunodeficiency Virus Infection (FAHI) and the Functional Assessment of Multiple Sclerosis (FAMS). These questionnaires were developed in North America and, to date, many have been translated into almost 30 languages. One of the strengths of this ongoing translation project is its use of input from patients, linguists, psychologists and physicians internationally to assure that the wording of Version 4 is more cross-culturally relevant and more sensitive to measuring the psychosocial impact of illness in cultures outside the United States. Statistical analysis, aggregation of patient comments, and comments from linguists and users of the translated versions are used as needed to revise item wording to ensure clarity and consistency across languages. A 'decentering' approach is also used to adapt the source (English language) document in response to problems encountered during its translation.