We investigated the prevalence and severity of dental fluorosis, and the occurrence of dental caries, among 12-yr-old children from high- and low-fluoride areas in a country with high caries figures and a developing oral healthcare system. The sample included a total of 600 lifetime residents from high-fluoride (HF; 1.7-2.2 ppm) and low-fluoride (LF; 0.2 ppm) areas in Lithuania. The diagnoses of dental fluorosis followed the Thylstrup-Fejerskov Index (TF), and a diagnosis of dental caries followed the World Health Organization criteria. In the HF area, 66% of the 12-yr-old children had dental fluorosis (TF score > 0) compared with 4% in the LF area. The maximum TF severity scores were 7 and 3, respectively. The mean number of teeth with fluorosis was 4.5 [95% confidence interval (CI) = 4.0, 5.0] for the HF group and 0.2 (95% CI = 0.1, 0.2) for the LF group. In the HF group, 72% had a decayed, missing or filled teeth (DMFT) score of > 0, compared with 87% in the LF group. The mean DMFT was 2.0 (95% CI = 1.8, 2.3) in the HF group and 3.5 (95% CI = 3.2, 3.8) in the LF group. Current untreated caries (DT) occurred (DT >0) in half of both the HF and LF groups. Regardless of the concentration of fluoride in the drinking water, the prevalence of past (DMFT > 0) and present (DT > 0) caries was high, calling for more emphasis on the prevention of tooth decay in countries, such as Lithuania, with high caries figures and a developing oral healthcare system.