4.1% of sudden cardiac deaths in the 16-64 age-group are unexplained. In this group, cardiac pathological findings are normal and toxicological tests are negative; termed sudden arrhythmic death syndrome (SADS). We searched for evidence of inherited cardiac disease in cases of SADS. Of 147 first-degree relatives of 32 people who died of SADS, 109 (74%) underwent cardiological assessment. Seven (22%) of the 32 families were diagnosed with inherited cardiac disease: four with long QT syndrome; one with non-structural cardiac electrophysiological disease; one with myotonic dystrophy; and one with hypertrophic cardiomyopathy. Families of people who die of SADS should be offered assessment in centres with experience of inherited cardiac disease.