At present, ventilation is measured in two different ways : Either"on-line"by analog gauges or"on-line"by sampling, with digital gauges. This paper describes the research done in developing an automatic digital system for continuous"on-line"measurement of cigarette ventilation at high speed. The theory of operation is based on three measurements for each cigarette, carried out under different conditions (open or closed end, reversed side air feeding). The individual ventilation of cigarettes is computed from the data.