Semifinal-round pairings for the Maryland and Virginia high school basketball tournaments were announced yesterday.

Williams, the Washington area's lone unbeaten team, will represent Northern Virginia in the AAA tournament at the University of Virginia in Charlottesville.

The Titans (26-0) will meet Henrico of Richmond (21-4) at 7 p.m. Thursday. The other semifinal game, between First Colonial of Virginia beach (22-2) and Roanoke's William Fleming (20-4) is at 8:45.

In Maryland, seven suburban Washington teams will be in the semifinals at the University of Maryland's Cole Field House Thursday and Friday. Four state final games will be played Saturday.

Thursday, Montgmery County class B champion Paint brance (22-3) will take on Francis Scott key of Union Bridge (24-1) while Thomas Stone (16-6) will meet North Hagerstown (19-4) in another class B contest.

In the feature AA contest, Blair (17-8) will play Baltimore County's Duloney (17-7). Blair won the 1975 title.

Friday, a second round of semifinal games will have Woodward (22-3) meeting Aberdeen (22-3) in a class A game and Prince George's AA tournament champion Potomac (20-5) taking on Annapolis (23-2).

Robinson will represent the Northern Region in the Virginia state AAA girls tournament at Fairfax Tuesday and Wednesday. The Rams will face Frank Cox High School of Virginia Beach in the 8 p.m. second semifinal.