Embattled Rep. Roy P. Dyson survived a strong challenge in eastern Maryland's 1st District Democratic primary and Republican Wayne T. Gilchrest defeated seven others vying for the GOP House nomination yesterday, setting up a rematch of the district's close race two years ago.

Dyson, a five-term incumbent who has suffered a long series of political setbacks, narrowly defeated Gilchrest in 1988, when the virtually unknown challenger capitalized on a groundswell of anti-Dyson sentiment. Gilchrest promised last night that this race will be even more hard-fought than the last.

In other Maryland congressional races, Prince George's County Rep. Steny H. Hoyer swamped Democratic challenger Abdul Alim Muhammad, but activists in each camp charged the other side with election irregularities. Republican Rep. Constance A. Morella in Montgomery County and Democratic Rep. Tom McMillen in the 4th District were renominated easily, as were the state's other incumbents.

Dyson, considered one of the country's most endangered House members, turned back an upset bid by Del. Barbara O. Kreamer of Harford County, who had hoped to capitalize on questions raised recently about Dyson's Vietnam-era draft exemption. With all the District's voted reported, Dyson had 54 percent and Kreamer 32 percent. Two other candidates split the remainder.

The predominantly rural 1st District sprawls from the Pennsylania state line to the state's southern tip, and Dyson ran strongest in Southern Maryland and the Eastern shore, his home area. But despite his incumbent status, he was rejected by a substantial minority of his own party members, a showing that left Gilchrest encouraged about his chances.

Dyson appeared before supporters at his campaign headquarters in Salisbury about 11 p.m. to claim victory, promising a vigorous fall campaign. "I feel confident enough to say it's on to November," he said.

"To my Republican opponent, who is obviously no stranger to us, I extend a hand of friendship," Dyson said. "I would hope that what we will do is have a very clean, positive campaign."

In the battle for the Republican nomination, Gilchrest, a Kent County educator, easily outdistanced his Republican rivals, none of whom had been able to create distinct images as voters confronted the crowded field. Gilchrest got 28 percent of the vote. His nearest challenger was Calvert County engineer Barry J. Sullivan, with 14 percent of the vote, followed by Calvert County Commissioner Mark Frazer and Del. Richard F. Colburn of Dorchester.

"I think we are going to take the seat," Gilchrest said from his campaign headquarters in Chestertown. "I have more name identification that I did two years ago, I'll be able to raise more money and the strength of the Republican Party has increased."

Dyson has been in almost constant political turmoil since early 1988. His troubles began when his top aide, Tom Pappas, committted suicide after questions were raised about his personal conduct and his management of Dyson's office.

Last year, Dyson refunded more than $10,000 worth of campaign contributions to donors who had been linked to a Pentagon procurement scandal. Last month, Dyson acknowledged that even though he has championed a strong defense and depended heavily on the defense industry for campaign funds, he was granted conscientious objector status during the Vietnam War.

In Prince George's County's 5th District, Hoyer lived up to predictions that he would handily defeat Muhammad, a first-time candidate and national spokesman for the Nation of Islam. With 125 of 140 precincts reporting, Hoyer had 80 percent to Muhammad's 20 percent.

But long before the polls closed, acrimony erupted. Muhammad supporters charged that voting machines had been tampered with, and county election officials said that in several instances, Muhammad supporters were ejected from polling places because they had attempted to intimidate voters.

The Hoyer-Muhammad race was being closely watched because Muhammad was trying to increase the political influence of the Nation of Islam and its leader, Louis Farrakhan, among the county's growing black population.

This is the first time that the Nation of Islam has fielded candidates in political races. Muhammad registered to vote in Prince George's County for the first time last spring.

James Conroy, a member of the county Board of Election Supervisors, said his group was investigating complaints that some Muhammad supporters had broken state law by campaigning within 100 feet of voting booths. "Some of this is due to inexperience and unfamiliarity with Maryland election laws, but some of it is just disruptive," Conroy said.