Abstract: Previous studies show that the hydroalcoholic extract of Pycnocycla spinosa is a relaxant of rat ileum and at the dose of 1 mg kg-1 inhibits diarrhoea in mice. Other studies indicate that P. spinosa extract has a selective pharmacological action to inhibit diarrhea. To use the P. spinosa extract as antidiarrhoeal, it is necessary to know the toxic effect on the kidney or live functions. Therefore, the aim of this study was to investigate the effect of oral administration of P. spinosa extract on renal function. Three groups of rats were orally given P. spinosa extract (1 and 10 mg kg-1 and vehicle) and then creatinine, uric acid, urea nitrogen and total protein concentration was measure in the serum and urine 24 h after treatment. Another three groups of rats were treated daily with similar doses of the extract for 14 successive dosing days and the same parameters were assessed. The results show that P. spinosa extract with dose of 1 mg kg-1 has no effect on serum and urine biochemical parameters such as urine creatinine, uric acid, urine nitrogen and total protein concentration after 24 h or 14 successive dosing days. At the dose of 10 mg kg-1 of P. spinosa extract, which is ten-times more potent than antidiarrhoeal dose, the urine total protein likely increased while no effects on other biochemical parameters were found. Therefore, from this study it could be concluded that the oral administration of P. spinosa extract at the antidiarrhoeal dose has no effect on rat renal function.