Updated

Missouri will allow medical-school graduates to work as "assistant physicians" and treat patients in underserved rural areas, though they haven't trained in residency programs, despite strong opposition from some doctors' groups.

At least one year of residency is usually required to practice medicine independently in the U.S.; most young doctors spend at least three years in such programs, which include intense on-the-job training and supervision.

Under the new law, signed by Missouri Gov. Jay Nixon last week, the medical-school graduates must be supervised in person by a collaborating physician for 30 days, and can then treat patients on their own as far as 50 miles away, and prescribe most medications. They must have passed the first two sections of the national licensing exam, though not the final one, and be approved by the state Board of Healing Arts, which issues medical licenses.

The Missouri State Medical Association, which represents the state's 6,500 physicians, helped draft the legislation, saying it was needed to address a severe shortage of health-care professionals. About one-fifth of Missouri residents lack adequate access to doctors, according to federal surveys.

"We felt it was time for someone to think outside the box and come up with a solution for rural health-care access, so that is what we did," said Jeffrey Howell, the group's director of government affairs.

Click for more from The Wall Street Journal.