THE AFL-CIO takes an enormous risk in readmitting the Teamsters. Its reasons for doing so are fairly obvious: labor is more powerful united than apart. The Teamsters are especially important -- with 1.7 million members they are the largest union in the country, reaching into almost every imaginable industry. The advantages of reunification are internal as well, since the aggressive Teamsters are always having jurisdictional disputes with other unions; these will be easier to compose with them in the federation than with them out.

The political schism between the Teamsters and the federation may in fact have been overdrawn. Teamster leaders have endorsed Republicans in recent presidential elections, but so have some AFL-CIO chieftains. On lesser elections and legislative questions the Teamsters and other unions have tended to work closely together anyway. The Teamsters also do pretty well -- very well -- at organizing and representing their members. The trucking industry is still their base, but they have diversified; their organizing ability is what has kept them large.

But this remains a special union. Everyone knows why. It has a long and richly documented relationship with organized crime. The corruption is what got it kicked out of the federation in the first place, 30 years ago. It is by no means clear the union has cleaned up; its president, Jackie Presser, is under indictment for embezzlement of union funds even as he prepares to takes his seat on the AFL-CIO executive council.

An indictment isn't guilt, and AFL-CIO President Lane Kirkland may be right in objecting to the tarring of the entire union with "collective guilt." But there is a burden associated with the readmission of this union as well as a gain. Labor may now be painfully emerging from one of its most difficult periods -- so Mr. Kirkland believes. The last thing it needs in such a circumstance is the tarnish that the Teamsters have so often brought in the past.

The federation, in gaining clout, also takes on a measure of responsibility for the Teamsters' future behavior. That is the risk on which this decision balances.