Gene flow from an experimental plot of genetically modified eucalypt was studied by measuring pollen dispersal at various distances from the pollen donor up to a maximum distance of 1592 m. Spontaneous seedling establishment around mother trees, the potential receptors of GM pollen, was also verified. All trees analyzed in this study were identified as compatible for crossing with the pollen donor and their flowering time frame showed at least two weeks synchronism with GM pollen donors. As reported in previous studies, pollination occurred at short distances then declined rapidly within 200 m. The results obtained are consistent with data from other reports in different conditions. In the current study, only two GM seedlings out of 574 were detected at distances greater than 300 m from source (one at 400 and the other at 857 m), in rates varying from zero to 1.5% until 857 m, and null above this. Although effective GM crossings were found in compatible trees around the pollen donors, no spontaneous seedling establishment was observed.