THE WORLD Health Organization is in the fortunate and, among United Nations agencies, unusual position of having a choice among several good candidates running for its top job. WHO deserves it. It's avoided the politicization and corruption that have brought other branches of the U.N. system into disrepute in the past. It's gone about its job of jacking up national health programs in ways that have brought it and its regional affiliates, such as the Pan American Health Organization, broad regard. On the new threat of AIDS, for instance, it is giving a necessary lead to the national health services, and its work with UNICEF on child-survival programs is crucial.

The director general for the last 12 years, a Dane named Dr. Halfdan Mahler, had planned to step down and had encouraged the head of PAHO, Dr. Carlyle Guerra de Macedo, a Brazilian, to run to replace him. Bloc voting is the style in these U.N. agency contests, and the Latins are backing Dr. Macedo. So is the United States. Three regional directors of WHO are also in the race. The election is in January.

Whoever wins will take over an organization that not only is respected professionally but also is recovering in a fashion -- not completely -- from financial hard times. WHO is one of those ''good'' U.N. agencies that were hit inadvertently but painfully by blows aimed at arms of the U.N. system that had gone sour politically or succumbed to mismanagement. The United States remains in substantial and unhappy arrears on its WHO assessments, but Congress seems to be in the process of anteing up for the current dues. Credit for this turn goes to the fact that a lot of people screamed, and Congress listened. These international agencies have tremendous burdens. Not so much goes right with them that the public should ignore it when it happens.