About 4,700 students from 98 different countries will mob the Yard tomorrow as dormitories open and Harvard Summer School's opening weekend begins.

This year's summer school will feature a revamped extracurricular activities program, which will include a new activities booklet and a fair for student organizations which will be held on Sunday.

"We will have representatives from various Cambridge groups and Harvard groups as well as our own summer school staff," said Liz Page Vrooman '88, assistant dean for activities at the summer school.

"We're offering much more extensive dance classes and exercise classes, aerobics, martial arts and ballroom dance classes," she added.

For the first time, some international students will attend a special four-week English program, which begins July 12. It will serve about 25 students who will all reside in Quincy House.

"A lot of high school students from other countries have expressed interest in learning English, but we haven't been able to accommodate them in the past because the [existing] program is geared to adults," said Susan E. McGee, registrar for the division of continuing education.

This year's most popular courses include tried-and-true favorites like general and organic chemistry, which have 102 and 162 students currently enrolled, respectively.

"There's a lot of interest in pre-med type course," McGee said. "The sciences are always strong."

Other courses attracting crowds include introductory law and psychology classes and a Shakespeare course taught by renowned Kenan Professor of English Marjorie Garber, which has 60 students enrolled.

Outside the classroom, summer school students can take trips to outlet mecca Freeport, Maine, as well as beach outings to Newport, R. I., Martha's Vineyard and Provincetown. The summer school will also offer trips to historic spots in Boston.

"There's just so much going on, so many things to enjoy in Boston," Vrooman said.

Massachusetts natives comprise 1,700 of the total enrollment, with New York, New Jersey and California sending over a hundred students each.

Some come to the College to meet Harvard requirements, with 300 students from the College and around 350 from other divisions of the University in attendance. Around 600 come to the program from other colleges, and severalthousand other students attend as members of thesecondary school program.

This year's student body also includes 106students from Japan, 83 from the Republic of Chinaand 67 from Brazil.

Just under half of the summer school studentsare expected to live in Harvard dormitories.

While secondary school program participantsusually live in the Yard, some will be housed inWinthrop House this year due to construction onYard dorms