Objective. This study investigated general practitioners' responses to three scenarios in which patients consulted regarding genetic conditions. Design. Self-completed postal study. Setting. Primary care in Northern Ireland. Subjects. Questionnaire were distributed to all the GPs in Northern Ireland (n=1079). A total of 541 GPs participated (50%). Main outcome measures. Responses to three scenarios in which patients consulted regarding their family history and risk of bowel cancer, breast cancer, and cystic fibrosis. Results. Most GPs correctly identified the patients' risk of bowel cancer, recommended regular colonoscopy, advised lifestyle changes, and did not refer to the genetic clinic. GPs who were qualified for longer were more likely to recommend colonoscopy and less likely to advise lifestyle changes. With the breast cancer patient GPs adopted a cautious approach; most would refer to the genetic and mammography clinics. With the cystic fibrosis example, most correctly identified the patient's risk of carrying the gene, would refer to the genetic clinic, and would encourage the patient to discuss the risk with his partner. In general, doctors were unsure, but would pass on genetic information to insurance companies if requested. Conclusion. The study suggests that, in most cases, general practitioners correctly identify at-risk individuals but there may still be some uncertainty regarding referrals. The results suggest that ways of educating GPs should be explored. Educational interventions should be linked to a greater understanding of factors involved in referral (including the influence of gender and experience). The guidelines provided to GPs in relation to the provision of genetic information to insurance companies may need to be reviewed in some countries.