During routine orthodontic screening in Oslo, Norway, of 3,157 children, aged 1--11 years and born in 1963/64, 36 cases (1.14%) with cosmetically marring discoloration of permanent front teeth were registered. Thirty-four of them arrived for a more exhaustive examination, which in 24 of the children revealed positive tetracycline fluorescence on exposure to ultraviolet light. In 13 (0.4%) of the children, the discolorations were diagnosed to be tetracycline-induced. Enamel hypoplasia was frequently found in teeth with positive fluorescence. Multiple exposures to various tetracyclines were reported in all children who exhibited positive fluorescence.