The main aim of this seven-year longitudinal study, of 411 Swedish pre-adolescent girls (aged 7-11 years, Year 1), was to examine a wish to be thinner, dieting attempts, described motives to be thinner and weight-control practices. A further aim was to examine to what extent body mass index (BMI) accounted for motives for wishing to be thinner and weight-control practices. A wish to be thinner and dieting attempts increased significantly with increasing age between the ages of 9 and 18. The most frequently reported motive for wishing to be thinner was to 'feel better about yourself'. Categories that emerged from the qualitative analysis of self-described motives for the wish to be thinner were, for example, to 'correspond to the societal ideal' and to 'wear particular clothes'. A majority of the girls adopted weight-control practices that would be considered as healthy, but extreme weight control practices increased with age. Girls with BMIs over the 75th percentile reported a greater number of motives for wishing to be thinner and used extreme weight-control practices significantly more often than the other girls. However, of the girls who changed BMI from above the 75th percentile to under the 75th percentile, 34,1% reported that they had not used any weight-control practices at all. Our results show that girls at a very early age are aware of the 'thin' ideal in our society, wish to be thinner and try to lose weight. The results point to the importance of detecting girls who wish to be thinner as early as possible. If we can employ preventive action in time, it is possible that dieting behaviour will never develop.