In somatic embryogenesis, embryo-like structures, which can develop into whole plants in a way analogous to zygotic embryos, are formed from somatic tissues. Somatic embryogenesis in pumpkin (Cucurbita pepo L.) can be obtained from mechanically wounded mature zygotic embryos cultured on media supplemented with 2,4D, but also on hormone-free medium containing NH4Cl as the sole source of nitrogen. Globular embryo stages predominate in media supplemented with NH4+ as the sole source of nitrogen and later-stage embryos in media with combination of reduced (NH4+) and unreduced (NO3-) forms of nitrogen. Developmental response of pumpkin embryogenic tissue to reduced and unreduced nitrogen supply was studied by measuring activities of two antioxidant enzymes - superoxide dismutase (SOD) and peroxidase. The activity of the latter was assayed with pyrogallol (PPOD) and guaiacol (GPOD). The enzyme activities were investigated after 4, 8 and 11 days of experiment. The results of the present study show correlation between antioxidant enzyme activities and developmental stages in embryogenic pumpkin lines grown in media supplemented with different forms and amount of nitrogen and growth regulators. Generally, SOD and PPOD activities increased in proembryogenic pumpkin tissue and decreased in embryogenic lines of pumpkin in which laterstages embryo predominated. Alternations in SOD and especially PPOD activities in pumpkin embryogenic cultures occurred in a stage-specific fashion and thus have a potential to function as early markers of somatic embryogenesis. Based on the SOD activity in tissues grown with different sources and amount of nitrogen, it was not possible to determine whether 1mM NH4Cl leads to oxidative stress because SOD activity was similar between different treatments.