Abstract: The common marmoset (Callithrix jacchus) is emerging as an increasingly desirable nonhuman primate model for many different biomedical studies, but animal numbers are limited creating a national shortage of high-quality marmosets available for biomedical research. The availability of an optimized sperm cryopreservation protocol will facilitate banking of gametes from each adult male so that it can then be used for other aspects of biomedical research. Here we propose to develop, optimize, confirm and validate the utility of such a protocol. We will optimize sperm collection method, sample dilution, cryoprotectant, extender, packaging, cooling/freezing conditions, and thawing conditions. Optimization will be based on assessment of frozen/thawed sperm in comparison with freshly ejaculated sperm for sperm count, viability, morphology, motility, sperm chromatin status, RNA content, genomic integrity and epigenetic profiling. Utility of the optimized protocols will be based on successful application at other marmoset centers. Successful optimization of a marmoset sperm cryopreservation protocol will greatly enhance the utility of individual male marmosets, while also greatly enhancing the ease and efficiency with which genetic diversity and/or specific genetic models can be distributed throughout the country or beyond.