Climatic change could bring about net release of carbon dioxide (CO2) and/or methane (CH4) from the deep peat deposits in northern peatlands into the atmosphere. To provide insight into this hypothesis, we studied net flux of CO2 and CH4 in Big Run Bog, West Virginia, which has a temperate climate, making it an analog to evaluate climatic change imposed on more northern counterparts. Net CO2 flux ranged from -564 to 300 mg C m-2 hr-1. Measurements made during the nighttime showed that net CO2 flux increased exponentially with increasing air temperature, whereas CO2 sequestration increased with increasing air temperature for daytime measurements. Net CH4 flux ranged from -2.3 to 70 mg C m-2 hr-1, showing no consistent relationship to temperature or water table level. Net efflux for both CO2 and CH4 was tenfold higher from peat cores incubated in a greenhouse compared to field measurements. Even cores drained and allowed to dry for 8 days showed moderately high flux for both CO2 and CH4. The enhanced efflux seemed to be due to altered hydrology rather than increased rates of bacterial production (measured in anoxic, in vitro incubations) which could account for only 50% of the whole-core flux. Presumably the remainder was CO2 and CH4 stored in the peat cores at the time of collection. Overall, the results suggest that a temperature climate imposed on northern peatlands could mobilize stored carbon and increase CO2 and CH4 efflux into the troposphere. Studies involving peat cores must insure that CO2 and CH4 dynamics measured in vitro mimic those in situ.