Objectives: To examine the relationship between this variation in the β1AR gene and the effect on LV mass. Background: Left ventricular (LV) mass is an important cardiovascular risk factor. Beta-1 adrenoceptors (β1AR) are predominately located in the heart and their variation may, therefore, affect LV mass. A known polymorphism of the β1AR changes the amino acid at position 389 from glycine to arginine within an area critical for G-protein coupling and so cell signalling. The arginine-form of the receptor has been demonstrated to have increased GTP binding. Methods: We studied 249 patients attending a renal clinic, 37 % of whom were on renal replacement therapy (RRT). Raw LV mass was calculated by echocardiography. LV mass index (LVMI) and LV mass indexed to height were derived thereafter. Individuals were genotyped for the β1AR variation and categorised CC if both alleles encoded for arginine at position 389, GG if both alleles encoded for glycine and CG if heterozygous. Results: There was a highly significant difference in raw LV mass, LV mass index and LV mass indexed to height between the GG group when compared to both the CC and CG genotypes groups (p<0.05). The strength of the relationship was maintained when patients on RRT or taking beta-blockers were excluded (p<0.05). Conclusions: These data suggest that genetic variation at this locus is of importance in defining left ventricular mass.