In 1989, a total of 674 pupils in the sixth and eighth grades in nine municipal schools in the Municipality of Frederiksberg replied to a questionnaire containing questions about health knowledge and behaviour. The behaviour of the pupils as regards tobacco, alcohol, diet, exercise, sleep, traffic, employment of medicine and general health were compared. In the sixth grade, 16% of the pupils and 48% of the pupils in the eighth grade had somewhat unsuitable behaviour as regards more than three of the above mentioned factors. In particular, girls in the eighth grade showed less suitable behaviour in several fields: many of these drank alcohol and smoked tobacco. In the eighth grade, several of the pupils had less suitable behaviour in the traffic than pupils in the sixth class. In addition, it was noted that over half of the pupils in both the grades involved had taken medicine within the past month. The majority of this medicine was for headaches. On the basis of these findings, the Medical Officers of Health for the Municipalities of Copenhagen and Frederiksberg have compiled a report in which they recommend that the schools under the local authority provide prophylactic measures against consumption of alcohol and tobacco and that these measures should be directed towards the girls, that the high consumption of medicine should be investigated further, that traffic drill for the older pupils should be considered and that prophylaxis of accidents during athletics both in schools and sports clubs should be included.