Sheep is a very important source of wool, meat and milk all over the world. Oxidative stress during in vitro culture leads to defects in development of gametes and embryos. Several antioxidants such as cysteamine, L-ascorbic acid, beta mercaptoethanol, cysteine, glutathione, proteins, vitamins are used to supplement culture media to counter the oxidative stress. This study was aimed to detect the effect of cysteamine supplementation to the maturation medium and oviductal cell supplementation to culture medium on the subsequent development rates of sheep embryos with the control group. Oocytes were obtained from slaughtered sheep ovaries. Selected oocytes were incubated with or without 100 mu M cysteamine in TCM-199 medium under 38.5-38.8 degrees C 5% CO2 for 23 h. During IVF fresh semen was collected from ram by electroejaculation, they were washed in H-SOF medium and were fertilized in B-SOF medium with oocytes incubated for 18 hours under 38.5-38.8 degrees C 5% CO2, 5% O-2 and 90% N-2. The oocytes were obtained from maturation medium with/without cysteamine (C+,-) and were cultured in SOF or CR1aa media with/without oviductal cells (Ov+,-) and were grouped as; Group Ia: SOF+(C+ Ov-), Group Ib: SOF+(C+ Ov+), Group Ic: SOF+(C-Ov-) Group Id: SOF+(C-Ov+); Group IIa: CR1aa+(C+ Ov-), Group IIb: CR1aa+(C+ Ov+), Group IIc: CR1aa+(C-Ov-), Group IId: CR1aa+(C-Ov+). Embryos were incubated under 38.5-38.8 degrees C 5% CO2, 5% O-2, 90% N-2 in culture medium for 7 days. Embryo developments were observed and recorded daily. GLM procedure found in SPSS packet program was used for statistical analysis in this study. In conclusion, the addition of cysteamine or oviductal cells in vitro culture media found to have any effect in terms of the capacity of reaching to blastocyst stage in SOF or CR1aa media and no statistical difference is detected between groups.