Kaiin EM, Prasetyo AT, Gunawan M, Setiatin ET, Ondho YS. 2020. Supplementation of follicular fluid into Garut sheep (Ovis aries) oocytes in vitro maturation media. Pros Sem Nas Masy Biodiv Indon 6: 532-536. The study was conducted to determine the effect of supplementation of sheep ovarian follicular fluid added to the oocyte maturation media on the rate of expansion of cumulus cells and the appearance of polar bodies I. Follicular fluid collected from the ovaries of Garut sheep and stored at -20°C before use. The treatment of adding follicular fluid with concentrations of 0 (control), 10, 20 and 30% in the M-199 maturation medium was used for in vitro maturation of sheep oocyte, then cultured in a 5% CO2 incubator with temperature 38.5oC for 22-24 hours. Sheep oocytes used were graded A and B with 7 replications. Data were analyzed by non-parametric statistical tests for Complete Random Design (CRD) and Duncan's follow-up test. The observation of the rate of expansion of cumulus cells showed no significant difference between treatments. Addition of Garut sheep ovarian follicular fluid in oocyte maturation media had a significant effect on the appearance of polar I bodies with the highest value (56%) in the treatment of 30% follicular fluid addition. Based on the results, it can be concluded that the addition of follicular fluid into the maturation medium influences the appearance of the polar I body which is the main characteristic of oocyte maturation.