Original article Prevalence of family history of colorectal cancer in the general population R. J. Mitchell 1,2 , H. Campbell 2 , S. M. Farrington 1 , D. H. Brewster 3 , M. E. M. Porteous 4 and M. G. Dunlop 1 1 Colon Cancer Genetics Group, University of Edinburgh, Division of Clinical and Molecular Medicine and Medical Research Council Human Genetics Unit, Western General Hospital, 2 Public Health Sciences, Department of Community Health Sciences, University of Edinburgh, 3 Information and Statistics Division, Common Services Agency for NHS Scotland and 4 Department of Clinical Genetics, University of Edinburgh, Western General Hospital, Edinburgh, UK Correspondence to: Professor M. G. Dunlop, Colon Cancer Genetics Group and Academic Coloproctology, Division of Oncology, School of Clinical and Molecular Medicine, MRC Human Genetics Unit, Western General Hospital, Edinburgh EH4 2XU, UK (e-mail: Malcolm.Dunlop@hgu.mrc.ac.uk) Background: Robust estimates of the prevalence of a family history of colorectal cancer in the general population are essential to inform planning of provision for colonoscopic surveillance and for clinical genetics services. However, there is a paucity of high-quality data. Methods: Computerized record linkage was used to assess systematically the family history of 160 cancer- free community subjects and thereby provide prevalence data that are independent of participant recall. The data set comprised 2664 first- and second-degree relatives of study subjects, with 148 068 years at risk. Results: Of people in the 30–70 years age range, 9·4 (95 per cent confidence interval (c.i.) 5·8 to 14·9) per cent had a first-degree relative affected by colorectal cancer, and 28·8 (95 per cent c.i. 22·3 to 36·2) per cent had an affected first- or second-degree relative. Between 0 and 3·1 per cent of study subjects merited colonic surveillance, depending on the stringency of the guidelines used. Conclusion: An appreciable proportion of the general population has a relative affected by colorectal cancer, sufficient to merit screening under certain criteria. In the absence of good-quality evidence supporting colonoscopic surveillance in groups at moderate risk, these data directly inform the planning of services for people with a family history of colorectal cancer. However, the clinical risk and financial implications of screening should be taken into account. Paper accepted 7 April 2005 Published online 4 July 2005 in Wiley InterScience (www.bjs.co.uk). DOI: 10.1002/bjs.5084 Introduction Empirical observations have shown conclusively that a family history of colorectal cancer is indicative of an increased personal risk of the disease 1 . Irrespective of whether this increased risk is genetic in origin or due to shared environment in the family home, the prevalence of a family history of colorectal cancer in the general population is of considerable clinical and public health importance. Such information not only contributes to an understanding of the causation of familial disease, but can also inform strategic implementation of preventive measures for population subgroups deemed to be at increased risk. Studies that address the prevalence of family history of colorectal cancer in the population generally rely on information provided by participants at interview or by questionnaire 2–4 . A recent study from this research group has shown that such data may be incomplete and unreliable, and must be interpreted with caution 5 . The objective of the present study was to estimate the population prevalence of a family history of colorectal cancer, using systematic interrogation of death records and the Scottish Cancer Registry to categorize the colorectal cancer status of individual family members. This approach provides complete information that is not influenced by interviewee recall bias, and offers qualitatively more robust data than have been available to date. Assessing family history of colorectal cancer in cancer-free subjects in this manner provides data on the prevalence of a family history of colorectal cancer in the community that helps Copyright  2005 British Journal of Surgery Society Ltd British Journal of Surgery 2005; 92: 1161–1164 Published by John Wiley & Sons Ltd