Temple University's School of Medicine announced Friday that it is expanding once again - in Pittsburgh.

It is collaborating with West Penn Allegheny Health System to establish a four-year medical campus.

Temple currently has a training program in Pittsburgh for third- and fourth-year medical students at West Penn Allegheny. Thirty students will be accepted into the new program, which is scheduled to start in 2013.

Temple's first class of 30 students at its other satellite medical school campus, in Bethlehem, will begin studies in August.

Larry Kaiser, dean of Temple's medical school, said doctors are more likely to begin practicing in the places where they train, so the outlying campuses will help attract doctors to Pittsburgh and the Lehigh Valley.

"This is to allow us to attract some students from Western Pennsylvania and to educate them, ideally in a place where they will stay and practice," he said.

Temple is one of seven schools in Pennsylvania that confer doctor of medicine degrees. There are also two osteopathic medical schools. New Jersey has three medical schools within the University of Medicine and Dentistry of New Jersey. A new school, Cooper Medical School, announced Thursday that it had received preliminary accreditation. It is scheduled to open in the summer of 2012.

The Association of American Medical Colleges estimates that there will be a shortage of 91,500 physicians by 2020 and 130,000 by 2025. Such forecasting is difficult, but the association says the country will need more doctors because the population is growing and aging, and because more people are likely to have health insurance coverage.

To meet the demand for doctors, many medical schools have accepted more students. Philadelphia College of Osteopathic Medicine opened a branch campus in Georgia in 2005. A new medical school, Commonwealth Medical College in Scranton, accepted its first class of students in 2009.

Nationally, the number of students in medical schools increased from 73,113 in 2006 to 79,070 last year. Area medical schools have expanded their classes as well.

Kaiser said the availability of government-supported residency slots for medical school grads is a looming issue. Residency positions have not expanded along with medical school growth. "There's going to have to be some additional [residency] spots created, but it doesn't look like the federal government's going to pay for it," he said.