SUMMARY1. Stroke‐prone spontaneously hypertensive rats (SHRSP) and normotensive Wistar Kyoto rats (WKY) were ‘chemically sympathectomized’ immediately after birth with 6‐hydroxydopamine (6‐OHDA, 100 mg/kg s.c. daily) for the first 10 days of life.2. Body weight gain was diminished in both groups as compared with sham‐treated controls. Blood pressure was reduced in ‘sympathectomized’ SHRSP, and also WKY rats had a slightly lower blood pressure than control rats.3. Plasma concentration of angotensin II and renin content of the kidney were not influenced by 6‐OHDA.4. ‘Sympathectomized’ SHRSP retained similar amounts of sodium than sham‐treated SHRSP when sodium retention is expressed per body weight gained. Plasma and blood volumes were increased in both SHRSP and WKY rats, whereas packed cell volume was significantly decreased.5. These results demonstrate the significance of an intact sympathetic nervous system for the development of hypertension in SHRSP. The expanded plasma and blood volume in ‘sympathectomized’ rats indicate an important role of the sympathetic nervous system and/or the arterial blood pressure for the regulat