Bromide concentrations were compared among Upper Permian and Jurassic salt rocks from various basins in the Western Interior. The Opeche salt (Guadalupian) from the Williston basin showed low concentrations of bromide, suggesting a strong nonmarine influence at the time of deposition. A Guadalupian salt from the Alliance basin showed values that fell in the normal marine range. Ochoan salts (Salado and Rustler Formations) from the Delaware basin, also showed normal marine values. The Jurassic Dunham Salt from the Williston basin contained no measurable bromide, suggesting that this is a second-cycle salt.--Modified journal abstract.