Parthenogenetic activation of mammalian oocytes with artificial stimuli is commonly applied in various reproductive biotechniques, e.g. cloning using nuclear transfer. We have described the activation of pig oocytes using nitric oxide. However, this activating stimulus is not adequate for parthenogenetic development. It was shown that nitric oxide stimulated some signalling pathways e.g. the cGMP-dependent signalling cascade. On the other hand, nitric oxide does not stimulate signalling pathways involved in oocyte activation after calcium ionophore, e.g. the PKC signalling cascade. In this review is characterized the complex processes induced in oocytes after treatment with nitric oxide and perspectives for further research and the application of nitric oxide are outlined.