en Original Article Original Article - Background: In the field of mammalian embryo culture, the putative influence of autocrine/ paracrine factor(s), produce by the embryos itself, is under investigation. A smaller medium drop can prevent dilution of this factor(s). Objective: The objective of this study was to examine the effect of culture medium volume on in vitro development of mouse 2-cell embryos. Materials and Methods: The embryos were obtained from female NMRI mice. To evaluate the effect of medium volume, groups of 16-20 late 2-cell embryos were cultured in 2, 5, 10, 20, 50 and 100 �l of drops of Ham�s F10 medium for 72 h. Results: Development to blastocyst stage in 50 and 100 �l of drop were significantly higher than this in any other volume (p<0.001). Almost a similar pattern was also observed for hatched blastocyst formation. However, the total number of cells in blastocysts, developing in different volumes, were not significantly different. Conclusion: These results indicate that the optimal volumes of Ham�s F10 medium for mouse early embryo development are 50 to 100 �l. However, volumes as small as 2 �l can successfully support mouse 2-cell embryo development to blastocyst and hatching stages. Mouse embryo, Culture medium, Incubation volume 79 82 http://ijrm.ir/browse.php?a_code=A-10-100-46&slc_lang=en&sid=1 Abbasali Karimpor Malekshah Yes Amir Esmailnejad Moghaddam No