Brines having moderate to high salt content (up to 343 grams per liter [g/L]) occupy most pore spaces in rocks below a depth of a few thousand feet in Pennsylvania and are brought to the surface during oil and gas operations. Forty analyses of brines from a range of geologic environments in western Pennsylvania are reported here, accompanied by brief descriptions of analytical methods required to obtain valid and accuratedata, especially for unstable parameters such as pH and oxidation state. The brines are dominated by Na-Ca-Cl.