At the end of folliculogenesis, ovulation delivers a fully differentiated oocyte bearing the haploid 2 DNA complement necessary for the construction of the zygote’s nucleus and the full cellular 3 machinery necessary for sustaining fertilisation, sperm head decondensation and early cleavage of 4 the resulting young embryo. The ability to undertake such a complex task is acquired gradually by 5 the oocyte during a very progressive differentiation process staggered all along folliculogenesis. 6 This process starts with oocyte growth during first steps of follicular development. Oocyte growth 7 is the most striking aspect of oocyte differentiation, resulting in the formation of the largest cell of 8 the body after a 300 fold increase in cytoplasmic volume. However, as the oocyte reaches a diameter 9 close to its final size, other modifications occur, less spectacular but at least as important in 10 determining the resulting ability of oocyte to accomplish its reproductive purpose. These important 11 modifications, referred to as «oocyte capacitation», are probably under follicular influence. Oocyte 12 maturation represents only the ending of this long and progressive process and validates the 13 preparation of the oocyte by conferring its final developmental ability. It is now clear that not all 14 oocytes are able to respond properly to one given culture system in maturation and these differences 15 may be attributed to different levels of oocyte capacitation, on the other hand, oocytes of 16 homogeneous initial status allotted to different maturation treatments will reach different 17 developmental competence levels indicating that appropriate maturation conditions are necessary for 18 the oocyte to express the developmental potential it has acquired during capacitation. Inadequate 19 oocyte capacitation and maturation of immature oocytes may represent the most limiting factor for 20 the use of assisted reproduction technologies in domestic species. Therefore, a better understanding 21 of these phenomena is required to improve in vitro embryo production in these species. This paper 22 reviews some factors influencing oocyte capacitation and maturation, how oocyte competence can be 23 measured and to what extent it could be influenced by follicular physiology and in vitro techniques. 24