The aim of the study was to investigate 1) the developmental potential of zona-manipulated oocytes (zona-free and zona-drilled oocytes and reconstituted oocytes) after in vitro fertilization (IVF); 2) the developmental potential of in vitro matured oocytes activated with either alcohol or strontium chloride (Srcl₂). Immature (germinal vesicle oocytes) and in vivo matured (ovulated) oocytes were collected from the ovaries and oviducts respectively and used during the study. Enucleated germinal vesicle (GV) oocytes were used as recipient of fetal fibroblasts for oocytes reconstruction. Immature and reconstructed oocytes were matured in vitro. Zona pellucida were either removed or drilled of some in vitro matured oocytes. The results showed that the zona-intact oocytes (in vitro matured) were not penetrated by spermatozoa after IVF whereas zona-manipulated oocytes (zona-free, zona-drilled and reconstituted oocytes) and in vivo matured oocytes were fertilized and cleaved. Although the reconstituted oocytes could not exceed two-cell stage embryos, the in vitro matured zona-free and zona-drilled oocytes as well as in vivo matured oocytes were cleaved further and developed to the blastocyst stage which markedly increased in the latter ones. Developmental potential to the blastocyst stage was higher of oocytes activated with strontium chloride (Srcl₂) compared with those activated with alcohol