Transgenesis is a complex process. Among the most important factors affecting the production of potential transgenic pigs using standard DNA microinjection into zygote pronuclei are the type of promoter used to express the gene construct and the method of zygote transfer used for transformation. The transformation of zygotes using different gene constructs showed that the promoter type influenced the developmental capability of the transformed zygotes, and this affected the percentage of born piglets. The transfer of transformed zygotes into a single oviduct resulted in a higher percentage of potential transgenic piglets born, this figure was almost doubled compared with transfer into both oviducts. Recently, research into the production of transgenic pigs has shown that factors connected with reproduction physiology and embryological factors such as the number of zygotes transferred after transformation and the season of the year have a significant influence but are not critical to the efficiency of production of transgenic pigs. The best results were obtained when less than 20 transformed zygotes per recipient were transplanted and the autumn season is the time when the environmental factors are optimal for production of potential transgenic pigs