The measure to allow physician-assisted suicide failed by a narrow margin, with 51% opposed.
While Oregon is the only state to have passed a law allowing doctor-assisted suicide, eight others are considering such legislation.
States have the power to allow and regulate assisted suicide, or to prohibit it.
While that measure never went into effect and was struck down last August, other legislation allowing assisted suicide is under consideration in several states.
This debate comes at the same time the administration is trying to strike down an Oregon law that allows physician-assisted suicide.
But surveys have shown that up to 50 percent of Catholics may vote to allow assisted suicide.
Oregon has passed a law allowing assisted suicide, but Republicans in Congress are trying to overturn it.
Here in Oregon, Catholic hospitals have already announced that they will not allow assisted suicide.
If it takes effect as scheduled on Dec. 8, the law will be the first in the nation to allow doctor-assisted suicide.
Switzerland is one of only a handful of countries worldwide to allow assisted suicide.