To prevent erosive tooth wear, early diagnosis and identification of causative factors are essential. The aim of the present 3-year longitudinal study was to investigate the association between a broad collection of biological and behavioural factors and the incidence and progression of erosive tooth wear among adolescents. The study sample consisted of 656 attendees of a dental clinic with at baseline a mean age of 11.9 years (SD = 0.9). The criteria for the assessment of erosive wear were a modification of the erosion criteria developed by Lussi [Eur J Oral Sci 1996;104:191–198]. Information on biological and behavioural factors was gathered by clinical examinations (at baseline, after 1.5 and 3 years) and by self-reported questionnaires (completed semi-annually). Of the erosion-free children at baseline, 24.2% developed erosive wear. In children with erosion at baseline, 68.3% showed progression. Multivariate analyses showed significant associations between the incidence of erosive tooth wear and alcoholic mixed drinks (odds ratio, OR = 1.82), sour vegetables (OR = 1.16) and tooth grinding (OR = 4.03). The intake of yoghurt products was significantly negatively associated with the incidence of erosive wear (OR = 0.79). The interaction of acidic products and tooth grinding showed a significant extra risk (OR = 1.2). The intake of vitamins was positively associated with progression (OR = 2.03). Erosive wear was less likely to progress in subjects who consumed milk and yoghurt products (OR = 0.89 and 0.76, respectively). The present study showed that the aetiology of erosive tooth wear is complex. Possible aetiological factors include more than acidic drinks, and factors such as tooth grinding play a large role.