The aim of Integrated Ocean Drilling Program Expedition 307 was to understand the origin and evolution of the coldwater coral banks in Porcupine Seabight off western Ireland, one of the most intensively studied provinces. Three sites were drilled on and near Challenger Mound in the Porcupine Seabight in May 2005, and core sections penetrating a thick coral reef body were recovered. To examine the thermal effect of possible upward hydrocarbon fluid flow beneath the mound, one of the hypotheses to be tested during Expedition 307, heat flow at and near the mound was calculated using data from Sites U1316, U1317, and U1318. These data were combined with previously published heat flow data in the neighboring region. Heat flow determined by this study is 56 mW/m2, which is in agreement with the values obtained during previous surveys and may support that there is no hydrocarbon fluid flow at Challenger Mound.