The composition and flux of gas emanations, and the isotopic ratios of CO₂, He and N₂ of 74 mineral springs and dry gas vents (mofettes) in the western Eger rift (Czech Republic) have been analyzed. Four geochemically similar, but tectonically separate, gas escape centers are distinguishable, out of which 3 show a free gas flux >85000 dm³ h⁻¹. All gases from the centers are CO₂-rich (>99 vol.%) and have δ¹³C values ranging from −1.8 to −4.0‰. ³He/⁴He ratios are as high as R/R_a = 5, and are among the highest measured in Europe. The discharge of the gas mixture decreases with distance from the emanation centers with both decreasing fractions of CO₂ and δ¹³C values, whereas the fractions of N₂ and trace gases increase. These changes in chemical and isotopic composition are associated by a decrease in R/R_a ratios from about 5 in the centers to <2 in the peripheries. The changes of the contents and isotopic composition of CO₂ can be explained by physico-chemical fractionations of CO₂ between gaseous and aqueous phases. Towards the periphery, the contents of free CO₂ and its δ¹³C are reduced by dissolution of CO₂ in groundwater, whereby the content of N₂ increases. ³He/⁴He ratios give evidence for mixing of He from both a deep-seated magmatic and a crustal source. The gas emanation centers, with their strongly magmatic δ¹³C value of about −2.7‰, seem to outline the intersections of the Eger rift and the Mariánské Lázně fault, which are considered to represent a deep-reaching fracture system that enables the ascent of gases from a magmatic body in the European subcontinental mantle (SCM). Therefore, the European SCM is suspected to be the main source of CO₂. The most mantle-like He (and probably N₂) occurs in the centers of gas release. The total regional gas flux in the western Eger rift is determined to be 3.6 × 10⁸ mol a⁻¹. When related to the investigated area of 1500 km², flux densities greater than 0.24 × 10⁶, 52, and 0.65 mol km⁻² a⁻¹ for CO₂, N₂ and He respectively are calculated.