FF-MAS and T-MAS sterols, intermediaries in the cholesterol biosynthetic pathway present in all cells, may represent the physiological signal that instructs the oocyte to reinitiate meiosis. The purpose of this study was to examine the hypothesis that exogenous lanosterol could be included in the sterol biosynthetic pathway from acetate to cholesterol and induce resumption of meiosis in oocytes cultured in vitro. Porcine oocytes were in vitro matured in medium supplemented with different concentrations of lanosterol. First, after 22h of in vitro maturation, cumulus cells were recovery and Delta7-Reductase gene expression was quantified using real-time PCR. Second, after 44h of in vitro maturation, chromatin configuration was evaluated using Hoechst 33342. Lipid content was also evaluated at 22 and 44h of in vitro maturation using Nile red staining. The results showed that the addition of lanosterol increased the Delta7-Reductase gene expression and influenced resumption of meiosis using 50 and 100microM, as well as enhancing higher cytoplasmic lipid accumulation after in vitro maturation. The results demonstrate that exogenous lanosterol acts in the sterol biosynthetic pathway from acetate to cholesterol and it was responsible for a higher resumption of meiosis in porcine oocytes cultured in vitro.