Despite the importance of the peer review process in research funding allocation, little has been reported on the levels of participation or the motivations of the scientific community in taking part in peer review. A survey focused on these questions was disseminated to scientists. Of the respondents, the majority indicated they had reviewed grant applications in the last 3 years; however, the number of reviews was unevenly distributed across this sample, with the top 10% reviewing 3 times the amount of the bottom 40% of respondents. The most prevalent reason to participate in a review was to give back to the scientific community and the most common reason to decline an invitation to review was lack of time. Interestingly, few suggested that expectation from the funding agency or honoraria was a motivation to review. Of those who reviewed, respondents reported dedicating 2-5% of their total annual work time to grant review and, based on their self-reported maximum review loads, it is estimated they are participating at 56%-89% of their capacity, which may have important implications regarding the sustainability of the system.