Terrence J. McAndrew was nearing retirement from the U.S. Postal Service in May when he walked into the office of a Montgomery County defense lawyer and made a startling confession.

Over the last seven years, McAndrew told the lawyer, he had embezzled at least $150,000 from the five House of Representatives post offices he managed. No one suspected that money was missing, but the theft was weighing on his conscience.

"As always happens, he started small and kept on doing it, and there was no one who caught him," said Paul F. Kemp, the lawyer who was approached by McAndrew and arranged for him to turn himself in to authorities. "I've never walked in with anybody who no one had any idea had committed a crime and said, 'Look, he committed a crime.' It goes against every fiber of my defense attorney body."

McAndrew, 56, of Rockville pleaded guilty Jan. 17 before U.S. District Judge Colleen Kollar-Kotelly to one count of misappropriating roughly $200,000 in postal funds.

He has repaid $150,000, his attorney said, with a balance of about $61,000 still in dispute with prosecutors.

Authorities said subsequent Postal Service audits have turned up more than $700,000 missing from the five post offices. But prosecutors said they believe that McAndrew worked alone, that they have accounted for all the money he stole and that the criminal investigation will end with his sentencing April 11.

Postal Service spokeswoman Molly McMin said yesterday that she did not have information to comment about the case or the audit findings. Other sources familiar with the investigation said it is unclear what happened to the rest of the money because Postal Service records are incomplete.

McAndrew, who has no prior criminal record, could face probation to 30 months' imprisonment. The married father of three, who had worked for the Postal Service for more than 30 years, secured his retirement before turning himself in and going on off-duty status in May, Kemp said.

"This is a straightforward case of theft and greed," said Mark H. Dubester, the District's assistant U.S. attorney with the fraud and public corruption section.

McAndrew was the senior on-site manager for the five post offices, which are tucked away in the bowels of the Capitol complex as a convenience to tens of thousands of Hill workers and lawmakers. The stores are similar to neighborhood post offices.

McAndrew handled cash and check deposits for the stores. He also gathered the vouchers that members of Congress use to pay for stamps and that are often for small amounts, such as $34 or $68 for 100 or 200 34-cent stamps. McAndrew would be reimbursed in U.S. Treasury checks for the vouchers by the House Office of Finance.

But he discovered that the Postal Service accounting system could not detect when he withdrew cash from bank deposits and substituted a Treasury check in the same amount, according to a Jan. 7 charging document.

He also used Treasury checks to cover money orders he made out in offsetting amounts to pay personal credit card bills and other expenses from January 1996 to May 2002, the charging document said.

Kemp said his client's need for money grew acute after osteoarthritis disabled his wife. "It was for a lot of reasons, family reasons, not for drugs, gambling or other women," Kemp said of McAndrew's motives.

"He couldn't live with it anymore. He felt so bad," Kemp said. "He's a very religious guy, a churchgoing guy. This is the one thing, kind of, he has ever done that was wrong. He got in and didn't know how to get out."

The episode raises a new cloud over an operation that Congress transferred to the Postal Service after a scandal in the 1990s. Former postmaster Robert V. Rota pleaded guilty in 1993 to conspiracy and embezzlement and said he had helped an undisclosed number of lawmakers embezzle tens of thousands of dollars over 20 years.

The ensuing investigation engulfed then-House Ways and Means Committee Chairman Dan Rostenkowski (D-Ill.), who was accused of stealing $21,300 by exchanging postal stamps for cash. Rostenkowski denied that charge but pleaded guilty in 1996 to two counts of mail fraud over the use of public funds to pay employees who did little or no work and to buy personal gifts. He served 17 months in prison before President Bill Clinton pardoned him in 2000.

Former representative Joseph P. Kolter (D-Pa.) was sentenced to six months in prison and fined $20,000 and the cost of his incarceration for pocketing $9,300 from the House Post Office and lying about it.

Rota and his staff were paid congressional workers under the supervision of lawmakers. After the scandal, GOP House leaders spun off the operation and turned over 13 retail outlets in House office buildings and the Capitol to the Postal Service for $1 a year.

A spokesman for House Administration Committee Chairman Robert W. Ney (R-Ohio) said in a statement, "The House cooperated with the Postal Service in its investigation, but at no point were House employees implicated in the investigation."

Staff researcher Julie Tate contributed to this report.