Elevated blood pressure is an important risk factor for renal-, cerebro- and cardiovascular diseases. We used an efficient discordant sib-pair ascertainment scheme to investigate the impact of the distal end of the long arm of human chromosome 5 (chromosomal region 5q31.1-qter) containing genes for the alpha1B and beta2 adrenergic receptors and the dopamine receptor type 1A on variation of systolic blood pressure in young Caucasians. We measured eight highly polymorphic markers spanning this positional candidate gene-rich region in 427 individuals from 55 three-generation pedigrees containing 69 discordant sibling pairs, and calculated multipoint identity by descent (MIBD) probabilities. The results of genetic linkage and association tests indicate that the region between markers D5S2093 and D5S462 is significantly linked to one or more polymorphic genes influencing interindividual variation in systolic blood pressure levels. Since the alpha1B adrenergic receptor and dopamine receptor type 1A genes are located close to these markers, these data suggest that genetic variation in one or both of these G protein-coupled receptors, which participate in the control of vascular tone, plays an important role in influencing interindividual variation in systolic blood pressure levels.