OBJECTIVE To evaluate the effects of Helicrysum ceres root and leaf extracts on mean arterial blood pressure and renal fluid and electrolyte handling in anesthetized male Sprague-Dawley rats. METHODS Cross sectional study. METHODS Departments of Physiology and Pharmacy, University of Zimbabwe. METHODS Eight separate groups comprising of control and treated Male Sprague-Dawley rats (n =6 in each group) were anesthetized and placed on a continuous jugular infusion of 0.077 M NaCl at 150 microL min(-1). The left carotid artery was cannulated with polythene tubing and then connected to a pressure transducer for blood pressure measurements. After 3 h equilibration period, consecutive 20 min urine collections and blood pressure measurements were made over the subsequent 4 h of 1 h 20 min control, 1 h treatment and I h 40 min post-equilibration periods for measurements of urine flow and Na+ and K+ excretion rates. Helichrysum ceres leaf extracts at 0.3, 0.6 and 1.2 microg min(-1) roots 0.3, 3 and 6 microg min(-1) were added to the infusate during the treatment period. To establish whether the extracts had activities comparable to drugs already in use, a separate group of animals was administered furosemide (0.12 microg min(-1)) during the treatment period. METHODS Hypotension, Natriuresis and Diuresis. RESULTS Infusion of graded doses of aqueous leaf extracts of Helicrysum ceres provoked an increase in urine flow rates but did not achieve statistical significance. However, the extracts produced dose dependent decrease in potassium excretion as well as increases in urinary Na+ outputs and diuresis. Administration of the various doses of aqueous root extracts of Helicrysum ceres significantly increased urine flow rate and urinary Na+ excretion in all groups. The intravenous (i.v.) administration of the aqueous root or leaf extracts of Helichrysum ceres significantly depressed mean arterial blood pressure (MAP). The diuretic and natriuretic effects of plant extracts were not significantly different to that of furosemide. CONCLUSIONS The results suggest that oral administration to rats of aqueous crude Helicrysum ceres root or leaves extracts induce hypotension and natriuresis.