Few well-controlled studies have investigated the impact of poor quality water on pig performance; fewer still have been conducted on commercial farms. While published research suggests pigs are capable of handling relatively high concentrations of sulphates and other mineral contaminants without apparent effect, field workers suggest that under farm conditions, the situation is different. Two experiments were conducted to determine how pigs react to poor quality water under commercial farm conditions. The animal performance results are presented in another paper in this Annual Report. However, blood and tissue samples were also collected and analysed to determine if the high sulphate and iron were affecting the pig in ways not revealed in performance studies. Similar to the performance data, the assay of blood and various organs failed to show any consisten changes due to water quality which could be associated with ill health or which could lead to production problems. These data confirm the ability of the pig to tolerate quite high levels of sulphate and iron in their drinking water without apparent problems at least within the time frame of this study. The modest changes in certain serum and tissue mineral levels, while not problematic, raise the question regarding the long term effects of exposure to high mineral levels in the drinking water.