To investigate the effect of a phosphodiesterase type 3 inhibitor in oocyte maturation medium on subsequent embryo development.Animal study.University laboratory.CD-1 mice.Immature oocytes were arrested meiotically in medium containing a specific phosphodiesterase type 3 inhibitor, cilostamide (1 μmol/L, 5 μmol/L, and 10 μmol/L), for 6 and 24 hours of prematuration culture, and then matured in vitro in inhibitor-free medium.Oocyte maturation, fertilization, and early embryonic development in vitro.After 6 and 24 hours of prematuration culture with 1 μmol/L, 5 μmol/L, and 10 μmol/L cilostamide, there were no differences in maturation, fertilization, and early embryonic development compared with non-arrested controls.Prematuration culture with cilostamide, for either 6 or 24 hours, may not be beneficial for subsequent embryonic development of immature mouse oocytes.