Although poppies (Papaver somniferum L.) are one of the oldest cultivated plants relatively little is known of their pollination biology. We have investigated the relative importance of wind and insects in the pollination of poppies and identified potential insect pollinators. Wind pollination was found to be negligible, insect pollination was responsible for the majority of out-crossing, and self-pollination was the dominant mode of poppy fertilisation. Honeybees and flies were identified as the main potential cross-pollinators of Tasmanian poppies. Using a transgenic poppy field trial in which approximately 50% of the pollen grains produced were transgenic, we have determined the level of pollen-mediated gene flow by scoring over 50 000 seeds for the presence of a selectable marker gene. Gene flow was measured using a 10-m buffer area that surrounded the field trial. It was highest at 0.1m with 3.26% of seeds found to be transgenic and declined over distance with 1.73% transgenic seeds at 0.5m, 1.80% at 1m, 0.86% at 2m, 0.34% at 5m, 0.12% at 9m, and 0.18% at 10m. These results demonstrate that under Tasmanian conditions, pollen-mediated gene flow occurs at modest levels in poppies that are in close proximity to each other and is most probably mediated by honeybees and flies.