Four persons were injured last night, two seriously, in an altercation in which a knife was used during a fund-raising dance attended by both students and nonstudents at Woodrow Wilson High School in upper Northwest Washington, police said.

A 21-year-old man, listed as unemployed, was arrested at the school at Nebraska Avenue and Chesapeake Street and charged with assault with a dangerous weapon, according to police.

Investigators said the altercation, which may have involved as many as eight or 10 pesons, broke out about 6 p.m. at the dance. It was held, according to Wilson's principal, to raise money for school supplies.

Detectives did not know what caused the altercation. About 200 persons attended the dance, including nonstudents who had obtained tickets from students at Wilson or other schools.

One of those injured seriously underwent surgery at the Washington Hospital Center for a stab would in the chest. He was identified only as Pridgin Henry, 21. Also listed in serious condition was Dana Roach, 18, who was operated on at Georgetown University Hospital for an unspecified injury on the upper right arm.

Derrik Mosley, 17, of 2306 13th Place NW, was treated at George Washington University Hospital for a slight stab wound on the left arm and was released, investigators said. David Boone, 20, was treated at Washington Hospital Center for a cut on the head, they reported. He was expected to be released.

Police identified the arrested suspect at Ricardo Cash, 21, of 2422 17th St. NW.