The isotopic proveniencing of human remains, using ratios of strontium, oxygen, and/or lead isotopes, has been employed in archaeology for more than two decades. The basic principles are essentially the same for the different elements and involve comparison of isotope ratios in human tooth enamel with local levels from the place of burial. Because isotopic ratios vary geographically, values in human teeth (place of birth) that differ from those of the local ratio (place of death) indicate movement and identify non-local individuals. However, there is often no easy answer to the question of where an individual came from because very distant and different places can have the same or similar isotopic ratios. To interpret the results, baseline values for isotopic ratios must be available from the place of discovery and also from potential places of origin. Estimates of isotopic ratios can be made for possible places of origin, either locations or regions, and bioavailable data can be collected to compare with human tooth enamel. Isotopic proveniencing cannot provide “proof” of a place of origin, only the possibility. This paper focuses on geographic variation in strontium and oxygen isotopes, specifically in terms of the bioavailable ratios present in the different parts of the North Atlantic study area. We provide a detailed overview of bioavailable isotope ratios. The discussion then moves to specific isotopic systems. The summary of strontium bioavailability is detailed from region to region, considering first the bedrock and surficial geology followed by an evaluation of bioavailable isotope ratios. We have also measured oxygen isotopes in human tooth enamel across the North Atlantic for comparison. Baseline oxygen isotope ratios are considered in a more general fashion in this paper because these vary at lower resolution across western Europe and a broader view is useful for understanding their distribution. We conclude with a synthesis of bioavailable isotope data for the North Atlantic.