[A self-administered questionnaire applied to 30,000 teen-agers. Assessment of this method of data collection (author's transl)].

In the French "département" of "Bas-Rhin", about 30,000 teen-agers filled in a self-administered questionnaire about respiratory symptoms, in spring 1976. The assessment of this method of data collection shows a very high response rate (99,7 p. cent). If we consider as incomplete all the questionnaires having at least one unanswered question concerning respiratory symptoms or smoking, 55,8 p. cent of them were incomplete, but for most questions non-response rate was lower than 4 p. cent. The consistency of answers was very satisfactory (mean inconsistency rate: 0,39 p. cent) and the likelihood of answers was proved.