The Organ Procurement and Transplantation Network (OPTN) maintains the national waiting list for available organs in the United States. The OPTN is the federally mandated system that coordinates all organ donation and transplantation across the country. For more than four decades, the United Network for Organ Sharing (UNOS) has operated the technology and day-to-day logistics behind that list as a federal contractor, running the matching system 24 hours a day, 365 days a year. As of 2025, over 103,000 people are on the national transplant waiting list.
How UNOS and the OPTN Work Together
The distinction between these two names confuses a lot of people, so here’s the short version: the OPTN is the system, and UNOS is the organization that has run it. In 1986, the U.S. Department of Health and Human Services awarded UNOS the very first federal OPTN contract. Since then, UNOS has built and maintained the computer systems that manage the waiting list and match donated organs to patients.
That arrangement is now changing. The Health Resources and Services Administration (HRSA), the federal agency that oversees the OPTN, launched a Modernization Initiative in 2025 to break the system into a multi-vendor model. Under this new structure, UNOS still operates the national matching system, but several functions it used to handle, including patient safety monitoring and tracking of potential disease transmission from donors, are being competitively awarded to other contractors. HRSA has also established an independent, elected OPTN Board of Directors that is separate from any contractor, and it moved registration fee collection from UNOS to direct federal management.
What the Waiting List Actually Tracks
The national waiting list is a computerized registry of every person in the United States who has been approved for an organ transplant but has not yet received one. When a donor organ becomes available anywhere in the country, the system instantly filters through the entire list to generate a ranked set of potential recipients. The computer excludes anyone who can’t physically receive that particular organ, then ranks the remaining candidates based on criteria specific to the organ type.
Blood type and organ size factor into every match. Beyond that, the criteria vary:
- Kidney: waiting time, how closely the donor and recipient immune systems match, whether the candidate is a child, prior living donation, distance from the donor hospital, and projected survival benefit.
- Heart: medical urgency and distance from the donor hospital.
- Lung: survival benefit, medical urgency, waiting time, and distance from the donor hospital.
- Liver: medical urgency and distance from the donor hospital.
Geography matters for every organ because transplant is time-sensitive. Organs can only be used if transplanted within hours of recovery, so candidates at transplant hospitals closer to the donor hospital generally receive priority.
How Patients Get Added to the List
You can’t add yourself to the waiting list directly. The process starts with a referral from your doctor to a transplant center, where a medical team evaluates whether a transplant is appropriate for your situation. Choosing the right transplant center matters: you’ll want to consider its location, whether your insurance covers procedures there, and what support services it offers.
If the transplant team determines you qualify, they add you to the OPTN waiting list. You should receive written confirmation about 10 days after being listed. Financial planning is also part of the process, since you’ll be responsible for any costs insurance doesn’t cover. Transplant centers typically have social workers and financial coordinators who can connect you with organizations that help cover transplant expenses. You can also register at more than one transplant center to potentially improve your chances, though each center will conduct its own evaluation.
How Children Are Prioritized
Federal law specifically requires the OPTN to recognize the differences in transplant issues between children and adults and to adopt policies addressing children’s unique health care needs. In practice, this means children get first consideration for organs donated by other children, because a properly sized organ is critical to a successful transplant. Pediatric candidates face additional barriers because their smaller size and developing anatomy limit the pool of organs that are anatomically compatible. The allocation system accounts for this by giving pediatric status extra weight in certain organ-matching formulas.
The Role of Regional Procurement Organizations
When someone in a hospital is identified as a potential organ donor, the local Organ Procurement Organization (OPO) is the first to respond. There are dozens of these nonprofit agencies across the country, each serving a specific region. The OPO evaluates the suitability of the donor’s organs, works with hospital staff to maintain organ function, coordinates with the family, and then enters the donor information into the OPTN system to trigger the matching process.
Once the system generates a ranked list of potential recipients, the OPO coordinates organ recovery surgery, preservation, and transport to the receiving transplant centers. This entire chain, from donor identification to organ delivery, relies on the OPO working in real time with the national matching system that UNOS operates.
Current Scale of the System
In 2024, the U.S. transplant system performed 48,149 organ transplants, a 3.3 percent increase over 2023 and a 23.3 percent jump over the previous five years. Of those, 41,119 came from deceased donors and 7,030 from living donors. Despite that growth, demand still far outpaces supply. With over 103,000 people currently on the waiting list, the gap between available organs and people who need them remains one of the most persistent challenges in American health care.