For an improved understanding of the gas-liquid contact system in an agitated vessel, it is very important to accumulate data about the bubble size distribution and interfacial area at all locations in the vessel. In this study, an advanced method is proposed for measuring the bubble volume and diameter equivalent to a sphere under high gas hold-up conditions based on the suction probe technique. This technique withdraws liquid containing bubbles from the vessel to the outside. It has already been elucidated in past studies by Greaves et al. The realtime high-speed image processing system, which was originally developed by the authors, is utilized as the measuring technique. It enables visualizing the entire image of a bubble distributed from about 30 mu m to 10 mm. Because this method can use a sampling tube with a diameter larger than that in conventional methods, it can be applied to viscous liquids and allows selection of sampling conditions without breaking the bubble during its flow in the tube, in contrast to conventional methods. The measured bubble diameter distribution data, specific surface area in various liquids, and examples of the relation between the conditions of agitation and the characteristics of the bubbles are presented. Using this method, quantitative information on bubbles in an aerated vessel with agitation is very accurate and is obtained in a very short time.