An extensive survey of well water used on swine farms in Saskatchewan was undertaken as a first step in trying to clarify the apparent disagreement between field and laboratory observations with respect to water quality and pig performance. One hundred and thirty-five wells throughout the province were sampled for a comprehensive chemical analysis; at the same time, a questionnaire concerning pig performance and perceptions of water quality was administered to the well owners. Concentrations of sulphate and total dissolved solids (TDS) were above levels recommended in Canada for livestock in 25.0% and 7.4%, respectively, of the wells. Sodium and chloride were also high in many wells. High levels of trace metals were not observed. Three major groups of wells were discerned: low saline, shallow wells with sulphate being the major contributor to TDS, high saline, deeper wells, also with sulphate being the major contributor to TDS, and high saline, deep wells with sodium the major contributor to TDS. The incidence of minor to moderate scouring in weanlings, as reported by producers, was directly related to TDS, magnesium, calcium and sulphate, but bore no relationship to sodium. The common occurrence of high sulphate water and its apparent link to on-farm scouring in weanlings indicate that sulphate is probably the ion of most concern to Saskatchewan hog producers. Key words: Well water quality, swine, sulphate, scouring