Housing and Urban Development Secretary Samuel R. Pierce Jr., the Cabinet's only black, is under fire for allegedly running a racist shop--a charge the secretary flatly denies.

The allegations surfaced in a lengthy, unsigned document that quickly made the rounds at HUD. The document detailed two dozen "case studies" of high-level black officials at HUD who had been removed, reassigned or RIFfed as a result of "both subtle and outright discrimination and racism."

The document charged that political appointees "have terrorized black career employes" with threats of adverse actions and poor performance ratings. The department, it complained, "has embarked on a campaign of blatant racism."

A copy of the broadside found its way to the office of Rep. Parren J. Mitchell (D-Md.), who wrote to Pierce in March asking for an explanation. The secretary responded in April that he was "personally affronted and disappointed by the document," which he characterized as an effort by "a few employes to hide behind allegations of racial discrimination."

Pierce called the allegations "either false or misleading," and noted that, of his 47 SES appointments, eight went to blacks.

But that didn't quite end the controversy. The HUD chapter of Blacks in Government submitted its own report to Pierce last month. Regina Hairston, head of the chapter, professes not to know who was behind the anonymous allegations, "but we looked into them and they were valid."

"I'll go with what has been charged--racism," she said.

According to Hairston, Pierce responded to the second document by calling his senior political staff in for a discussion. "He informed them of what was going on, told them to be more sensitive, place blacks in ad hoc committees and task forces," she said.

She said the blacks had seen no "concrete results" as yet, but Pierce "appears to be very open about it. All I can do is to wait, as he instructed. You can't change things overnight."