We performed a genomewide scan with 904 microsatellite markers using 120 extended Icelandic families with 490 hypertensive patients. The families were identified by cross-matching a list of hypertensive patients from the Hypertension Clinic of the University Hospital (Landspitalinn) in Iceland with a genealogy database of the entire Icelandic nation. After adding 5 markers, we found linkage to chromosome 18q with an allele-sharing LOD score of 4.60 (P=2.1× 10−6). These results provide evidence for a novel susceptibility gene for essential hypertension on chromosome 18q and show that it is possible to study the genetics of essential hypertension without stratifying by subphenotypes.