The extent of embryonic death in preimplantation period in the pig may reach even 40%. Several factors contribute to this phenomenon (onset of oestrogen production, uterine space, chromosomal inbalance). The aim of the present study was to clarify whether genetic sex influences the development of pig embryos in the preimplantation period since the already published data is not consistent. Porcine embryos were flushed out post mortem on day-10 after insemination, photographed and individually frozen. DNA was extracted from 91 embryos and sex examined by use of PCR method with pair of primers corresponding to the SRY gene. 94.5% of embryos were succesfully sexed. Embryonic perimeter was measured by means of computer aided programme and sexed embryos were classified and grouped into three categories: small, medium and large, accorrding to their perimeter. According to statistical analysis, embryonic size was not influenced by genetic sex. The overal sex ratio, females to males (1.4:1) was not significantly different from the expected 1:1. Moreover, no significant difference between the percentage of males and females was found in the three categories.