Quality of life (QOL) assessments that are easily administered and which do not impose a great burden on the respondent are needed for use in large epidemiological surveys, clinical settings and clinical trials. Using data from the WHOQOL-BREF field trials, the objectives of this work are to examine the performance of the WHOQOL-BREF as an integrated instrument, and to test its main psychometric properties. The WHOQOL-BREF is a 26-item version of the WHOQOL-100 assessment. Its psychometric properties were analysed using cross-sectional data obtained from a survey of adults carried out in 23 countries (n = 11,830). Sick and well respondents were sampled from the general population, as well as from hospital, rehabilitation and primary care settings, serving patients with physical and mental disorders and with respect to quotas of important socio-demographic variables. The WHOQOL-BREF self-assessment was completed, together with socio-demographic and health status questions. Analyses of internal consistency, item-total correlations, discriminant validity and construct validity through confirmatory factor analysis, indicate that the WHOQOL-BREF has good to excellent psychometric properties of reliability and performs well in preliminary tests of validity. These results indicate that overall, the WHOQOL-BREF is a sound, cross-culturally valid assessment of QOL, as reflected by its four domains: physical, psychological, social and environment.