This report lists water quality stations operated by the Geological Survey for what data are available in machine-readable form. The data are the results of analyses of water samples and indicate the chemical and physical characteristics of surface and ground water. The stations are listed according to station number within each State. The water quality data are identified by 5-digit parameter codes and are grouped into twenty-one parameter categories. The analytical results for all samples in any one year are then grouped within the parameter categories. The report lists the available retrieval options, the machine-readable output options user charges, and how to obtain the data.