Two doctors on trial in Montgomery County Circuit Court for billing the state for some $6,000 worth of treatments they allegedly never performed on poor patients contend the billings were proper, but not complete, because of the large volume of patients they handled.

Lawyers for Dr. James L. Hooper, 50, of Sandy Spring, and Dr. Melvin Kordon, 45, of Columbia, said in court yesterday that the doctors were among the few who would accept indigent patients under the Medicaid program. Consequently, their patient loads were high during 1972-77, the period when the disputed billings were submitted and when they worked at the Deer Park Medical Group in Gaithersburg.

The case was brought by the Medicaid fraud control unit of the Maryland attorney general's office, one of 30 such units across the country. Dr. Hooper's attorney, James R. Miller, told the jury the case began when another doctor had a disagreement with the Gaithersburg medical group and took her allegations of fraud to the Maryland attorney general.

The two doctors were charged with 330 counts of false pretenses on Nov. 25, 1980.

Dale P. Kelberman, an assistant Maryland attorney general, said the government examined 750 of the doctors'15,000 reimbursement claims for office visits in 1980. The amount claimed was between $6 and $12 for each visit. Of those examined, 330 had no entries in the patients' medical records to support the claim, he said.

"The evidence will show that the defendants . . . instructed their employes to submit the claims with the intent to defraud the state of Maryland . . . of$6,000," Kelberman said.

Miller, Hooper's attorney, said Hooper and his three associate physicians often treated as many as 150 patients a day.

"In many instances, a patient's regular files could not be found, so employes would make a temporary record, with plans to eventually transfer information to the regular file," Miller said. As a result, full documentation behind a claim often was not found in every patient's file, he explained.

In addition, Miller said that shortly after Medicaid began, doctors were allowed to submit bills for some work done earlier. " That policy might be where some of the problems in this case came from," Miller said.

After the indictments were issued, Miller said his client discovered he had not billed the state for $12,000 worth of treatments, $4,000 of which now has been paid.

Attorney Alan Baron, representing Kordon, told Judge John J. Mitchell that the charges "have put my client's professional career and his reputation on the line.

"Dr. Kordon is a fine doctor, a fine man, a devoted man," Baron said. He said that Kordon left the Deer Park Medical Group in 1977 to open his own family practice, 10 percent of which is devoted to indigent care.

Under Maryland law, a conviction for false pretenses carries an unspecified fine and a jail term of two to 10 years.

In its three years of operation, 31 physicians have been convicted of charges brought by the Maryland Medicaid fraud control unit. Three doctors have been acquitted, according to Andrew Tartaglino, its director.