Objective:To investigate the diuretic and renal effects of Silybum marianum L. and Cistus ladaniferus L. in normal rats. Methods:Four groups of rats were used in each experiment. The first group received water, the second group received Cistus ladaniferus L. extract (100 mg/kg b.wt), the third group received Silybum marianum L. extract (100 mg/kg b.wt), and the fourth group received furosemide (10 mg/kg b.wt). Variables including urine volume, plasma and urine sodium, potassium and creatinine, and creatinine clearance were measured. Two experiments were conducted. A single dose of each intervention was used and the variables were measured during 24 h, and the interventions were given daily for a total of 8 d and the variables were measured during various intervals. Results:The single dose of each plant extract increased urine volume at all-time intervals and increased urine sodium and potassium excretion without affecting plasma sodium and potassium (P<0.05). On the day 8 after daily administration, the plant extracts induced a significant diuresis and natriuresis without affecting serum electrolytes (P<0.05), while furosemide caused hypokalemia. Both plant extracts significantly increased creatinine clearance (P<0.05). Conclusions:Silybum marianum L. and Cistus ladaniferus L. increase creatinine clearance and have a significant diuretic effect without affecting serum electrolytes. Silybum marianum L. is more potent than furosemide or Cistus ladaniferus L.