Helium isotopic and rare gas measurements in the Dogger aquifer of the Paris Basin have shown the helium concentration and helium isotopic ratio to be first-order homogeneous with only slight differences in relation to specific chemical water types. Helium in the Dogger aquifer contains quantities of 3He 3--4 times in excess of radiogenic production/accumulation from natural decay of U, Th series elements. Calculations of cosmogenic production/accumulation of 3He cannot account for the observed excesses, and 3He excess is attributed to the addition of a mantle-derived He magmatic component. Calculations of the isotopic fluxes of helium out of the Dogger <4He flux, 2¿10-7 mol 4He m-2 yr-1; 3He flux, 1.8¿10-14 mol 3He m-2 yr-1 (¿50%)> suggest that the helium residence time and the groundwater residence time in the Dogger aquifer are 4 Myr (¿50%). This age estimate is at least 10 times as great as estimates derived from hydrologic models but is more consistent with the geochemistry of the water. ¿ American Geophysical Union 1993