The quality of an irrigation water depends upon the kind and amount of salts that are dissolved in it. A chemical analysis will show what salts are present and in what amount. From such an analysis, it is possible to decide on the suitability of the water for irrigation use. The purposes of this publication are: 1. To describe the characteristics of an irrigation water that determine its quality. 2. To indicate the type of water analysis that is required. 3. To show how to judge quality from the water analysis.