OBJECTIVES: To identify the extent to which the Cochrane Collaboration involves consumers (patients, carers, patient and non-patient members of patient/consumer organizations) as members of Cochrane Review Groups (CRGs); to explore the emphasis CRGs place on identifying and collecting information on outcomes identified by patients as being important indicators of quality and effectiveness of treatment and care ('patient-defined outcomes'). METHOD: A postal questionnaire designed by The College of Health, a UK patient organization, was sent in January 1998 to all CRGs registered with the Cochrane Collaboration on 1 January 1998 (n = 42). RESULTS AND CONCLUSIONS: Replies were received from 35 CRGs, a response rate of 83% and 33 questionnaires (79%) were completed. The survey revealed that CRGs varied in the extent to which they had recruited consumer members: almost one third of respondents said their CRG did not have any consumer members. There was also no apparent consensus across CRGs on the importance attached to identifying and collecting information on patient-defined outcomes or on integrating such information into their activities. It is hoped that differences between CRGs may inform discussions as to whether and how the Cochrane Collaboration might address the issue of patient-defined outcomes in the future.