Slow or insufficient enrollment in clinical research and a high demand for research participants raises questions about the need for and use of incentives to participate, including payment. Much of the available literature on payment to research participants focuses on ethical concerns, and rarely addresses guidelines, benchmarks, or formulas to assist investigators to assign or evaluate appropriate payment for individuals who take part in clinical research trials and procedures. Using four years of data collected about the inconvenience units assigned by intramural investigators to selected clinical research procedures conducted at the National Institutes of Health (NIH) Clinical Center, this study provides payment benchmarks for commonly performed procedures. Results were obtained from data collected on 36,273 incidents of payment made for procedures to research participants from August 2004 to August 2008. Analysis of the inconvenience units value assigned to specific procedures suggests that despite a wide distribution and frequent outliers, a convergence in practice around the center of distribution for most procedures does exist. As one of the first published studies reporting data reflecting payment amount for specific clinical research procedures, these data can guide investigators and institutional review boards as they establish and review an appropriate amount of payment to offer research participants. Our data may be useful in promoting payment standards for procedures, thereby complementing proposals or guidelines that advise payment calculations according to time and procedures.