Objective: To determine saponin contents of different parts of Tribulus terrestris L. growing at different time

and so as to determine the best harvesting time and the possibility of the aerial parts for clinical use. Method: The absorption of the sample solution was measured at 310 nm and the saponin contents were calculated against sarsasapogenin by spectrophotometry. Result: From July to October the total saponin reaches the highest amount in July for stems and leaves

October for fruits and July for aerial whole parts. Conclusion: From the point of view of total sapoin contents

from July to October the stems and leaves or aerial parts of T. terrestris should be harvested in July while fruits in October. Furthermore

the feasibility of the aerial parts of T. terrestris for clinical use is also manifested.