At their entry to training, student teachers and nurses (pupils, general students and paediatric students) completed a questionnaire and were interviewed about their knowledge and opinion of smoking as a health hazard. This was repeated a year later. The nurses and student teachers did not differ in their knowledge of eight smoking-related diseases at their entry to training, but the nurses were less willing to acknowledge the importance of smoking as a health problem. This was in part related to differences in their smoking behaviour, smokers being less likely to perceive smoking as a hazard than non-smokers. Smokers were also more likely to express doubts about the role of smoking in illness. In general at entry the pupil nurses were the least likely to accept that smoking is harmful to health. After a year of training little change was evident among the student teachers. Among the nurses knowledge had improved for some conditions and decreased for others. Improved knowledge was most evident among the general students but scores declined consistently among the pupils. The uptake of knowledge was also related to the nurses' smoking behaviour, non-smokers tending to become better informed and smokers less certain. In general, the nurses had also become less likely to acknowledge the importance of smoking as a health issue, and again, this was most marked among the pupils. Smoking behaviour did not account for these changes. The nurses applied their training experience to their views, the effect usually being to confirm existing ideas. Not all experience had a positive impact and training had not enhanced understanding of the causal relationship between smoking and illness. One explanation could lie in the way the subject of smoking is dealt with during teaching.