The galactic evolution of the abundances of the light-element isotopes (6Li, 7Li, 9Be, 10B, and 11B) is re-examined in view of recent measurements of the 7Li/6Li interstellar isotopic ratio. The high value of this ratio (≡40), found by Ferlet and Dennefeld (1984) towards ζ Oph, can be reproduced by simultaneously including contributions to the nucleosynthesis of 7Li by galactic cosmic rays, red giants, and novae. Good agreement with the observed abundances and isotopic ratios is also obtained for the other elements. The results show that low-energy cosmic rays should play only a minor role in galactic Li Be B production, and also that a pregalactic abundance of Li/H ≡ 10-9 does not present a good fit to present-day values as well as to Solar-System ones.