A 32-year-old man who had been a resident physician at Prince George's General Hospital since last July was arrested last week after hospital officials said they learned that he had never graduated from medical school.

Rafael Montano of Greenbelt, who was a first-year resident in the hospital's family practice program, was arrested by county police Thursday after hospital officials said they learned that he was dismissed from a Mexican medical school during his first year there. He has been fired from his job at the hospital, officials said.

A hospital official said that Montano was told several weeks ago that his contract would not be renewed in July because of poor performance. Suspicion about him was aroused recently, the official said, after he apparently applied to another hospital and a doctor in California called Prince George's General to verify a letter of recommendation submitted for Montano.

An official in the county prosecutor's office said Montano was charged with theft on the ground that he had been paid as a physician after making the allegedly false representation that he was a physician. James Xinis, associate director of the hospital, said Montano received an $18,000 salary as a first-year resident.

Montano was held in the county detention center Thursday night and released Friday on his own recognizance. He could not be reached yesterday for comment. An attorney for the hospital said that as a first-year resident Montano worked under close supervision, and that as far as the lawyer knew, no formal complaints have been made against him by patients.

Family practice, the area in which Montano was working and being trained, was described by the lawyer as a specialty most akin to the work of the general practitioner.

The lawyer, Michael P. DeGeorge, said that physicians in the hospital's family practice clinics generally see patients with relatively routine complaints. All entries made by Montano on patients' charts were routinely countersigned and reviewed by more experienced physicians, DeGeorge said. Hospital officials said that Montano's work was primarily diagnostic and that he performed no surgery.

Based on his application for the residency program, Xinis said, hospital officials understood that Montano had graduated from medical school in Guadalajara, Mexico.

Xinis said the application also indicated that Montano held a California medical license and had completed a year of training at a hospital in Los Angeles.

Applicants for the program undergo a "very detailed" screening process, Xinis said.

He provided no details on the system by which credentials are verified.

Montano's application "is one apparently that may have slipped through the cracks," according to DeGeorge, the hospital's lawyer.

After entering the residency program last July, Xinis said, Montano received poor evaluations from the physicians supervising him, and "was told several weeks ago that his contract at the hospital was not going to be renewed because of poor performance throughout the year." After being called recently by a California doctor to verify a letter of recommendation in Montano's behalf, Xinis said, the hospital "looked through his file and learned that his documents were false."

In a confrontation with a superior at the hospital, Xinis said, Montano "admitted that he had never graduated from medical school."

After questions arose, hospital officials said, Montano was suspended, and on Thursday, they said, police were called and he was arrested.

He was brought before a commissioner Thursday on a charge of theft and bond was set at $10,000, according to official records.

However, after a bond review hearing, Montano was released on his own recognizance Friday, according to officials at the county detention center.

Repeated unsuccessful attempts were made yesterday to reach Montano. No further details were available from police or prosecutors.