1. The aim of the present study was to scan chromosome 1 in the hypertensive 'inherited stress-induced arterial hypertension' (ISIAH) rat strain for the quantitative trait loci (QTL) that control basal and stress-induced arterial blood pressure (ABP) levels and weight traits. 2. Two F(2) populations of 3-4- and 6-month-old male rats derived from a cross between the normotensive Wistar albino Glaxo (WAG) and hypertensive ISIAH rats were used in the search for the QTL. To identify the QTL for blood pressure (basal and under stress) and weight traits (bodyweight, as well as the weight of the adrenals, kidney and heart), 12 polymorphic markers covering a span of 234.6 Mb on chromosome 1 were analysed. 3. In 3-4-month-old rats, QTL were found for bodyweight in the vicinity of the D1Rat76 marker (230.6 Mb; P = 0.0019; logarithm of odds (LOD) score 3.23) and for relative kidney weight in the vicinity of the D1Rat117 marker (219.3 Mb; P = 0.000992; LOD score 3.41). No QTL for blood pressure were detected on chromosome 1 in the 3-4-month-old population. 4. In 6-month-old rats, a QTL for basal ABP in the region spanning 168.0-250.4 Mb, with two peaks around the markers D1Rat168 (204.8 Mb; P = 0.00087; LOD score 3.42) and D1Rat76 (P = 0.0006; LOD score 3.34), was described. A novel QTL was found in the D1Rat54-D1Rat168 region for stress-induced blood pressure (P = 0.0014; LOD score 3.08). 5. The results provide support for the existence of age-dependent differences in the genetic control of ABP and weight traits. Chromosome 1 was characterized by four QTL: for bodyweight and relative kidney weight in 3-4-month-old F(2) (ISIAH yen WAG) rats and basal ABP and ABP under emotional (restraint) stress conditions in 6-month-old F(2) rats. The QTL for stress-induced ABP seems to be novel and specific to the ISIAH rat strain.