A 20 per cent increase in the number of applications has forced the Medical School to delay mailing its letters of acceptance and rejection until February 15, a month later than usual.

Since medical schools may begin to demand deposits after January 15, the delay means that applicants to Harvard Med have had to place deposits else-where or gamble on acceptance here.

This deposit, according to a spokesman for the Association of American Medical Colleges in Evanston, III., may not exceed $100. Some medical schools, such as Harvard, demand no deposit.

There have been 1421 applications for 125 places in the Medical School this year, compared to 1192 applications last year, a spokesman for Dr. Perry J. Culver, director of admissions, said.

In a letter to all applicants earlier this month, Culver pointed out that Harvard is not obligated to complete action on applicants by January 15, although it has been the School's policy to do so.

Davis Johnson, director of the division of student affairs of the AAMC, said that most medical schools do not think of January 15 as a deadline for action as Harvard does. He said that a study showed that one out of three students accepted to medical school in 1965 received the offer he eventually accepted after that date. "It surprised us that Harvard bothered to write the letter," he concluded.

Culver wrote to the applicants that Harvard's policy has been "to make every effort" to notify all candidates by January 15, but it was impossible this year because of "a great increase in the number of qualified applicants."

Culver's office had no idea how many applicants have decided to put down a deposit to hold a place in another school. An applicant who decided to gamble faces mathematical odds of more than 11 to 1.

The executive director of the AAMC, Dr. Robert C. Person, said he does not know of any other medical schools which have delayed their admissions process this year.

The Medical School is one of only three Harvard graduate schools which has had an increase in applications this year. The others are the Divinity School and the School of Education.