In the second year of operating an Early Action admissions program, Harvard and Radcliffe have admitted 510 students to the Class of '82, William R. Fitzsimmons '67, director of admissions, said yesterday.

Over 1900 high school seniors applied under the program, an increase of about 400 over last year. The 510 students already accepted make up about one-fourth of the Class of '82.

Under Harvard's Early Action program, part of an early notification plan adopted throughout the Ivy League in 1976, the Admissions Office notifies early admissions candidates of their acceptance, rejection, or deferral by January 1. Accepted applicants have until May 1 to reply to the office. The number of students admitted under the program rose from 439 to this year's 510.

Fitzsimmons attributed the increase to the sharp jump in number of early applications that stemmed from "an increased knowledge of the Early Action option as well as what it means for the student." Noting that students who apply early face no additional admissions criteria, Fitzsimmons said the program is "a service to applicants to relieve the tremendous amount of anxiety" of college applications.

The Admissions Committee has deferred 1068 early applications until the regular mid-April notification date. Fitzsimmons said those applications will receive equal consideration with the pool of students applying by the regular January 1 deadline.

The committee rejected 187 applicants.

Yale and Princeton, who along with Brown have Early Action programs identical to Harvard's, also showed increases in the number of applications, although their applicant totals were far smaller than Harvard's.

Jeanne C. Davis, director of research of undergraduate admissions at Yale, said yesterday 1292 applicants sought early action at Yale this year, an increase of 150 over last year. The school accepted 473 applicants.

Princeton accepted 330 of 1201 students who applied under the program, Timothy C. Kallard, director of admissions at Princeton, said yesterday. He added that the percentage of students applying from public school increased significantly over last year, as the program has received greater publicity.

This year's Harvard Early Action program "attracted a stronger pool of students" than either last year's early or regular applicants, Fitzsimmons said.

He added that the yield in early applicants admitted to the Class of '82 was higher than that of normal applicants. The make-up the group Harvard accepted "did not reflect any unusual trends," Fitzsimmons said, although it appears to indicate that minority group members tend to wait until the regular January deadline to apply.