Understanding the patterns of distribution of plant genetic resources, especially the extent and contextual bases of distributions, may be critical in setting appropriate targets for seed multiplication, packaging, storage space, and other technical operations. We analyzed germplasm distribution patterns over a 12-year period for 10 crop collections conserved by the North Central Regional Plant Introduction Station in Ames, Iowa, to determine if distribution rates over a given time interval help predict future distributions and to document how distribution patterns vary among accessions within collections. We demonstrated that, with an appropriate tracking system and commonly available statistical software, germplasm distribution patterns can be easily analyzed and plotted over time. Data measured over periods of up to 3 years had little predictive value, while a 6-year period gave relatively accurate projections of future distributions. Patterns of distributions within collections varied between those that are approximately normally distributed and those best described by an exponential function, with larger collections tending to be non-normally distributed. Means and standard deviations of standardized, long-term distribution rates, calculated from samples of 200–700 accessions, accurately described the distributional rates of 90–95% of all accessions. The documentation of changes in usage patterns within and among collections as they mature is also discussed. Analysis of average shipment size suggests that germplasm distributions became more focused over time for 8 of the 10 collections analyzed. This may result when users request germplasm based upon knowledge about specific accessions gained through personal experience and by examining evaluation and characterization data.