IN THE COURSE OF his unfortunate directorship of Washington's Department of Human Resources, Joseph P. Yeldell quite naturally developed a store of helpful professional contacts - people around the town with whom his huge city agency might do business as well as others to whom he might turn for certain special kinds of assistance. Millionaire developer Dominic Antonelli apparently fell into both categories. Indeed, it is this coincidence of interests that now happens to be under investigation by federal prosecutors. There's no telling what the results of this investigation will be, but the relationship of the two men should be of concern to taxpayers nonetheless.

From what is known so far, here are some of the byproducts of the Yeldell-Antonelli relationship:

In 1973, according to Mr. Yeldell, he was first introduced to Mr. Antonelli, who had earlier contributed to Mr. Yeldell's unsuccessful campaign to be the city's delegate to the House.

In addition to his city job, Mr. Yeldell had a private travel business, which he operated with six associates and which was in debt. The business (now defunct) managed to obtain a $21,500 loan arranged by Mr. Antonelli from Madison National Bank, in which Mr. Antonelli is a major stockholder.

Between 1973 and 1976, Mr. Yeldell (1) urged the city to sign a 20-year, $5.6 million lease on an office building that Mr. Antonelli had just purchased for $800.000, (2) urged a shift in the site of a hospital in which Mr. Antonelli had a financial interest to a property owned by Mr. Antonelli, and (3) sought city funds to buy a downtown hotel in which Mr. Antonelli also had a financial interest.

In 1976, Mr. Yeldell sought some personal financial advice from Mr. Antonelli. That produced a loan of $33,000, arranged by Mr.Antonelli through an intermediary, according to a news account in this newspaper. It was a second-mortgage loan, at 8 per cent interest - at a time when other lenders in this area were charging 10 to 12 per cent.

Now, without prejudging the legal aspects under investigation, this is the sort of relationship that top government official ought to take pains to avoid. By receiving personal financial assistance of this magnitude from someone for whom his city government agency is in a position to arrange vast profit, Mr. Yeldell here again showed his intensitivity to the public responsibility entrusted to him. Since Mayor Washington too fails to recognize this fundamental weakness in his administration, we trust the federal prosecutors will pursue the Yeldell investigation vigorously.