ObjectiveTo determine the level of understanding of personal genetic risk in people born with a one in two risk of having autosomal dominant polycystic kidney disease (ADPKD).DesignConsenting individuals, contacted through affected family members, were asked standard questions about their knowledge of their own genetic risk. These questions were incorporated into a study investigating the use of DNA diagnostic techniques in ADPKD which was an opportunity to interview a substantial number of Australians at risk of inheriting this condition.SettingInterviews were conducted in the individuals' homes, or at the Royal Melbourne Hospital Renal Clinic or the Royal Children's Hospital Genetics Clinic.PatientsThree hundred and eighty‐seven individuals aged 15 years or more, born with a one in two risk but who had remained undiagnosed up until the time of the study were identified within 46 families. Sixty‐six were excluded from the study either because they resided too far away or they declined involvement. The remaining 321 were assessed clinically, 304 of whom were also interviewed about their understanding of their risk of having inherited this condition.ResultsThirty per cent knew their risk at birth was one in two. Nine per cent were unaware that ADPKD was an inherited condition. Forty‐one per cent were aware that ADPKD was inherited but had no opinion about their personal risk. Three per cent thought that they had no chance of having the condition, 3% thought that they were definitely affected, 8% considered their risk lay from 1%‐49% and 6% thought their risk lay from 51%‐99%.ConclusionWithin this group of people with a high risk of having an Inherited condition with preventable and treatable components, the majority has a poor understanding of their genetic risk.