The solubility of the gypsum is generally very high in comparison to many other minerals. The surface and groundwater contacting gypsum formations can easily attain high amounts of total dissolved solids (TDS), calcium, and sulphate. This composition of the waters prevent their usage for drinking, domestic, industrial and irrigation purposes. Gypsum formations, containing halite (rock salt) interlayers, crop out in a large area in Upper Kizilirmak basin, Sivas, Turkey. In this study, the effects of the lithological composition of the catchment area on the water chemistry and quality were studied on the Upper Kizilirmak basin. Surface waters draining gypsiferous area, and Goydun and Seyfe springs create high TDS concentration in Kizilirmak river (EC = 1100-5200 muS cm(-1)). Goydun and Seyfe springs which issue from gypsum are very rich in TDS (EC = 12 825-13 900 muS cm(-1)) and are of poor quality. Surface and groundwater resources in non-gypsiferous part of the basin (Yildiz river, Kaynarca and Gazikoy springs, Tavra valley) have lower TDS and higher quality. EC of these waters range between 495-630, 795-995, and 530-575 muS cm(-1), respectively. The Kizilirmak river (with the exception of the upstream part which drains non-gypsiferous area), Goydun and Seyfe springs, and the well in Kizilirmak river alluvium (SK-1) are not suitable for drinking, irrigation and industry. TDS, hardness, sulphate and chloride concentrations of these waters exceed maximum permissible limits for these parameters in Turkish Drinking Water Standards (TDWS). The above mentioned water resources have high to very high salinity and sodium (alkali) hazard from the point of irrigation water quality, and are not also suitable for allmost all industrial usage.