The International Brotherhood of Teamsters has been selected as bargaining agent for D.C. Corrections Department employes, soundly defeating the incumbent union in a representation election and giving the Teamsters their first major foothold among city workers here.

In balloting yesterday at Lorton Reformatory and the D.C. Jail, the Teamsters won 59 percent of the vote, while the American Federation of Government Employees (AFL-CIO), which has represented corrections workers here for 30 years, received 41 percent.

"We think it's a big victory for us," Teamsters coordinator James Panos said last night. "We are probably going to go after other labor units in the D.C. area. The international is very interested in that."

For AFGE, the loss of the 2,400-member Corrections Department unit was a severe blow, reducing by nearly a third the number of city government employes it represents. Mary Lynn Walker, a trustee of AFGE Local 1550, said the union will "consider everything" before deciding whether to challenge the election results.

Voting was heavy, with 1,879 employes, or about 78 percent of those eligible, casting ballots, according to Donald H. Weinberg, head of the D.C. Office of Labor Relations. He said the Teamsters received 993 votes, the AFGE got 700, and 186 votes were challenged for various reasons.

Weinberg said it was unclear why so many votes had been disallowed. Since their number was not large enough to swing the results back to AFGE's favor, however, the Teamsters Union was declared the winner.

Teamsters coordinator Panos said he was "elated" at the outcome, which was the culmination an expensive, hard-fought and frequently bitter campaign that was waged for more than a year.

"Our immediate plans are to get proposals from people and elect shop stewards and start bargaining with the city as soon as possible" about wages and benefits, better working conditions and new promotion procedures, he said.

Panos said that a pay raise granted to prison workers by Mayor Marion Barry last Saturday had "no effect" on yesterday's voting. Teamster officials had previously called the timing of the 10 percent raise an attempt by the city to "steal the election" for the AFGE.

"We are going to push for pay parity" with the police department, Panos added. "They [AFGE negotiators] got the crumbs, but we're going for the cake."

An additional union objective, he said, "is to try to straighten out the overcrowding problem" at the D.C. Jail. He said the union will study all the alternatives before deciding whether to support construction of a new jail.

AFGE's Walker said that one factor in the defeat of her union is that "working conditions are very, very poor in the jail," where the inmate population is scheduled to be reduced by 800 in the next 90 days, according to an agreement reached last Thursday between a U.S. District Court judge and the city.

The challenge to AFGE's leadership was mounted last year with the onset of widespread dissatisfaction among corrections officers, some of whom complained that the union was not tough enough in its dealings with the city.

The AFGE's problems grew so severe that the union's Washington headquarters took over the local and installed temporary officers, citing "mismanagement" and "undemocratic practices."

In the summer of 1984, the Fraternal Order of Police, bargaining agent for the city's rank-and-file police officers, presented the District's Public Employees Relations Board (PERB) with a petition signed by more than half the city's corrections employes saying that they wanted to change unions.

The Teamsters also collected signatures and filed a petition, forcing a three-way runoff.

Faced with a stiff leadership challenge, AFGE countered by collecting signatures and -- along with the International Brotherhood of Police -- forced a representation election in the police department.

Barry tried to prevent both elections by arguing that -- in the case of AFGE and the FOP -- the same union should not represent both police and prison employes because of the potential conflict of interest if workers at the jail or Lorton Reformatory went on strike and police were called in to replace them.

The PERB overruled the mayor's objections, and the issue became moot when in February the FOP won a landslide victory in the police department election but came in last in the Corrections Department vote. In that election, however, neither the AFGE nor the Teamsters won a majority of the votes cast, forcing a runoff last March.

When the ballots were counted from that election, the Teamsters won by three votes of 1,525 votes cast, and AFGE challenged the victory, claiming that about 40 nonunion workers had cast ballots.

In June the PERB ordered a new election, which set the stage for yesterday's rematch.