Narrator: This is Science Today. Many difficult ethical issues have come up in the field of organ transplantation. Dr. John Roberts, chief of transplant services at the University of California, San Francisco, says because of a lack of donors, one of the main issues is deciding how to allocate organs.

Roberts: As the demand for transplantation increases, we're really left with these issues about how do we get organs distributed fairly or with justice?

Narrator: With limited resources, a philosophy called triage often comes into play.

Roberts: There's sort of wartime triage and there's peacetime triage. Peacetime triage generally occurs in situations where you have enough of a resource, you just have to figure out who needs to go first. Where, wartime triage is you just say, I can't take care of this guy - let him die. That's sort of the battlefield triage kind of system and one that transplantation, particularly of the life-saving organs, heart and liver is sort of been moving toward.

Narrator: For Science Today, I'm Larissa Branin.