In the present work, a gamma-ray attenuation technique was used to measure gas holdup distribution in stirred tanks. Measurements have been carried out in a 0.57-m-i.d. tank agitated by a pitched blade downflow turbine (PBTD45degrees) and a disk turbine under two different conditions, namely, surface aeration and sparger aeration beneath the impeller. The measurements have been made at various operating speeds. In both the cases, the average gas holdup calculated by integration of the local gas holdup was found to match well with those obtained by visual observations based on volume expansion. The gas holdup profiles also enable identification of speeds of regime transition. This technique appears to be promising for the characterization of industrial stirred reactors.