The aim of the study was to compare the effectiveness of calcium gluconate and cabergoline therapy in the prevention of ovarian hyperstimulation syndrome (OHSS). Eight hundred and forty-five women who underwent GnRH antagonist protocol and at high risk for developing OHSS were divided into two groups, those given cabergoline (n=435) or calcium gluconate (n=410). In cabergoline group, 0.5 mg of cabergoline was administered once daily p.o. starting on the day of ovulation trigger and continued until the following 8 days. In calcium gluconate group, intravenous calcium gluconate was administered daily for four days starting on the day of oocyte pickup (OPU). 10 ml of 10% calcium gluconate solution was dissolved in 200 ml of physiological saline and administered by intravenous route within 40 minutes. Infusion was started within the first 30 minutes following the OPU and continued on the 1st, 2nd and 3rd days after OPU. Mild OHSS was developed in 367 (89%) patients receiving calcium gluconate infusion, while 251 patients (57%) in the cabergoline group developed mild OHSS. The frequency of mild OHSS in the calcium group was significantly higher than the cabergoline group (p<.001). Moderate OHSS was observed in 32 people (7.8%) in the calcium gluconate group, while it was observed in 184 people in the cabergoline group (42.3%). Calcium gluconate infusion significantly reduced the development of moderate OHSS compared to cabergoline therapy (p<.001). Severe OHSS developed in 11 patients (2.7%) in the calcium gluconate group, while severe OHSS did not develop in those given cabergoline (0%, p<.001). Clinical pregnancy, live birth and abortion rates were similar in the two groups. When logistic regression analysis was performed, a significant correlation was found between age, BMI, AMH, the number of antral follicle count, OHSS history, paracentesis, progesterone on the day of hCG, 2 PN zygotes, and HbA1c levels and the development of OHSS. No correlation was found between the use of metformin or cetrotide and the development of OHSS. Calcium gluconate treatment is not effective in the prevention of OHSS.