To better understand the genetic basis of essential hypertension, we conducted a quantitative trait locus (QTL) analysis of a population of 207 (BALB/cJ x CBA/CaJ) F(2) male mice to identify genomic regions that regulate blood pressure, heart rate, and heart weight. We identified two loci, Bpq6 (blood pressure quantitative locus 6) on chromosome 15 (Chr 15; peak, 16 cM; 95% confidence interval, 0-25 cM) and Bpq7 on Chr 7 (peak, 42 cM; 95% confidence interval, 35-50 cM) that were significantly associated with blood pressure. We also identified two loci, Hrq1 (heart rate quantitative locus 1) and Hrq2, on D2Mit304 (peak, 72 cM; 95% confidence interval 60-80 cM) and D15Mit184 (peak, 25 cM; 95% confidence interval 20-35 cM), respectively, that were significantly associated with heart rate. A significant gene-gene interaction for heart rate was found between Hrq1 and D1Mit10 (peak, 57 cM; 95% confidence interval, 45-75 cM); the latter QTL was named Hrq3. We identified a significant locus for heart weight, Hwq1 (heart weight quantitative locus 1), at D14Mit67 (peak, 38 cM; 95% confidence interval, 20-43 cM). Identification of the genes for these QTL should lead to a better understanding of the causes of essential hypertension.