The results of a one-year study of the total air-borne14C effluents from two Swedish light-water reactors, one boiling water reactor (BWR) at Forsmark and one pressurized water reactor (PWR) at Ringhals, are presented. Air emitted from the stacks has been collected continuously over two-week periods and the14C content in the samples has been analysed using accelerator mass spectrometry (AMS). The14C activity concentration in the air issuing from the stack of the PWR varied between 2 and 1132 Bq/m3 with a mean value of 200 Bq/m3, while from the BWR the activity concentration varied between 4 and 146 Bq/m3, with a mean value of 95 Bq/m3. The corresponding14C release rate was 0.27 TBq/GWel·year for the PWR and 0.48 TBq/GWel·year for the BWR. During the same period of time, for comparison, the14C activity in continuously collected air from the stack of the PWR was also measured by liquid scintillation counting. In most cases the results of these measurements were in fair agreement with the corresponding AMS results.