The aim of the study was to follow a group of pupils from the age of twelve until they leave lower secondary school at the age of sixteen to describe and analyse how their attitudes towards and intere... mer st in science and technology develop and change but also how this and other factors such as ability, understanding of scientific concepts, gender and home background influenced their choice for upper secondary school. The sample consists of 80 pupils, the whole age group in a school. Data was collected using observations, interviews and questionnaires. The analysis built on the theory of planned behaviour and conceptions research. Many pupils have a positive attitude towards science but often a more positive attitude towards other subjects. They have duties to their parents but these are not strongly expressed. Their self-efficacy for science follows the same pattern as their attitude; they think they are good in science but not as good as in other subjects. For most pupils it seems as if attitude together with self-efficacy are the strongest determinant for their choice. These determinants are influenced by different factors. Girls and boys perceive science teaching differently but it seems as if the boys are on their way to developing the same critical attitude as the girls have had since long ago. The social background is important as many of the pupils who choose science are from well educated homes but even this group is loosing interest. Good ability is a necessary factor but does not guarantee science will be chosen. Neither has good conceptual understanding a crucial importance but on the other hand there are many pupils who say that they would not choose science as they do not understand science in the way it is taught. Another finding is that many pupils even at Grade 5 have an idea of their future career which later on is the same as their choice for upper secondary. If science shall have a chance in their lives the pupils must have a positive experience of science from the beginning of primary school through all years. Once they have lost their interest it is very difficult to get them back. The competition for their attention is intensive and the older they get the more difficult it will be to catch their interest and allegiance.