Studying temporal changes in genetic diversity depends upon the availability of comparable time series data. Plant genetic resource collections provide snapshots of the diversity that existed at the time of collecting and provide a baseline against which to compare subsequent observations. The International Board for Plant Genetic Resources conducted collecting missions in 136 countries mainly between 1975 and 1995, with the result that over 200,000 samples of a wide range of taxa were collected and distributed to genebanks around the world for long-term conservation and use. Twenty-seven percent of the collected samples were crop wild relatives and 61 % were landraces. Given their age, geographic and taxonomic scope, these collections have great potential value for establishing historical baselines for monitoring the status of conservation or the erosion of genetic diversity. This article reports on efforts to ‘chase down’ those samples and to confirm their conservation status and whether they are publicly available. For 35 % of the materials, we were able to recreate a unique link between original passport data and other collecting documentation (collecting sheets and reports) with extant accessions held in genebanks. This information enables a number of important uses, ranging from the identification of potential duplicates in genebanks and the assessment of effectiveness of ex situ conservation procedures to the re-collecting and assessing of genetic erosion and temporal variation in landraces and crop wild relatives.