The study was performed to compare the efficacy of a herbal plant, Orthosiphon grandiflorus (OG), and the drug sodium potassium citrate (SPC) in treatment of renal calculi. Forty-eight rural stone formers identified by ultrasonography were recruited and randomly assigned to two treatment groups (G1 and G2). For a period up to 18 months, subjects in G1 received 2 cups of OG tea daily, each tea cup made from an OG tea bag (contained 2.5 g dry wt), and G2 received 5-10 g of granular SPC in solution divided into three times a day. Once every 5 to 7 weeks, subjects were interviewed, given an additional drug supply, administered a kidney ultrasound and had spot urine samples collected for relevant biochemical analysis. From the recorded ultrasound images, rates of stone size reduction per year (ROSRPY) were calculated. The mean ROSRPY was 28.6±16.0% and 33.8±23.6% for G1 and G2, respectively. These two means were not significantly different. ROSRPY values of G1 and G2 were combined and divided into three levels: Level A (ROSRPY > mean + 0.5 SD), Level M (ROSRPY = mean ± 0.5 SD) and Level B (ROSRPY < mean - 0.5 SD). Dissolution of stones was least in Level B which was related to higher excretions of Ca and uric acid in the urine. After treatment, 90% of the initial clinical symptoms (ie back pain, headaches and joint pain) were relieved. Fatigue and loss of appetite were observed in 26.3% of G2 subjects. Our study indicates that treatment of renal calculi with OG tea is an alternative means of management. Further investigation is needed to improve dissolution of stones with a low ROSRPY.