Swimmers, for several hours a week in contact with pool-water, may develop two different types of pool-water related oral conditions: dental erosion and dental staining. Dental erosion may occur when the acidity of the pool-water is below a pH-value of 5, dental staining when the pH-value of the pool-water is above 6.5. Of the two conditions mentioned, dental erosion is the most harmful, because it involves an irreversible process. The clinical significance is clarified by a few case-reports. In Dutch pools, the pH-value of the pool-water has to be checked daily. Therefore, among Dutch swimmers there is only a slight possibility of arising oral conditions caused by pool-water.