Students at most medical schools spend the first two years of their training in lectures and labs, passively soaking up information about "basic" medical sciences such as anatomy and biochemistry. But this year, on their first day at Harvard Medical School, 24 new students began their studies with a case drawn from life.

Faced with a man suffering a cardiac arrest in a theater, their professors asked, what would they do? What would they want to know? Where would they go to learn more about the causes of his heart disease ?

With no more medical knowledge than the average person, the students developed a list of questions inspired by the case. They asked about the chances of surviving cardiac arrest, the complications of a heart attack, the importance of risk factors like smoking and stress and the impact of sudden death on surviving family members. Then they set out to answer their own questions, using the library, personal computers and experts on the Harvard faculty.

The 24 are the first to travel the New Pathway, Harvard's radical new approach to training doctors. The experimental program, launched by Harvard Medical School dean Daniel C. Tosteson, is a response to the explosion of new medical information, the increasing importance of cost in medical decisions and the public's demand for more sensitive and socially aware physicians.

Its purpose: to produce humane doctors who will be lifelong learners.

"It's time for a new reformation in the way medical students are taught," said Dr. Alvin Tarlov, president of the Kaiser Family Foundation, which contributed $3 million to help implement the new curriculum.

Added Tosteson, "We look upon it very much as a prototype and are actually discussing . . . the pace of extension throughout the student body."The New Pathway abandons the traditional division of sciences into separate courses. Instead, classes cross subject boundaries. Gross and microscopic anatomy, radiology and the technique of the physical exam are combined in "The Body," the new curriculum's first twelve-week block. Other first-year courses also have strikingly untraditional titles, such as Life Cycle, Identity and Defense, Patient/Doctor, Information Processing and Behavior.

Lectures are limited to one hour a day. For the rest of the morning, students meet in groups of six -- often with two or three professors teaching each class. All teaching centers on cases, which may involve patients or problems to be solved. The teachers' role is not to lecture, but to lead a discussion in which students explore what they know and decide what they need to find out. Most afternoons are left free for independent work on the questions raised by the sessions.

Elements of the program have been tried at other medical schools, but Tosteson said Harvard is "the first traditional, research-based school to make a commitment to this kind of learning.

One worry of some faculty members is whether the case-oriented curriculum will impart all the facts needed to be a competent doctor, or to pass the first part of the National Board examination, a science test required by many states for licensure, which students take after two years of medical school.

Anatomy professor Daniel Goodenough said a test administered at the end of the first twelve weeks suggested New Pathway students were learning as many facts as the rest of the first-year class, which is still taught by the lecture system. But it will be several years before the educational success of the program can be evaluated.

The students "know what they know and what they need to know to a surprising degree," said Dr. Gordon Moore, the program's director.

Although the seminar format often is more time-consuming for teachers, many say they relish the close contact with students.

Under the old system, lecturers "deliver these Gilbert and Sullivan patter songs" packed with facts, said Goodenough. "Many of us have no idea what students need to know in order to be good physicians . . . We're wasting our time by singing these patter songs. They're wasting their time by cramming and forgetting . . . and in the process, they become very alienated from us."

But in New Pathway classes, he said, "You hear them use the words, you hear them work with the concepts . . . Every faculty member who's come in contact with these students has come away starry-eyed."Students are equally enthusiastic. All 165 in the 1985 entering class received information on the New Pathway last March. Seventy-five asked to participate; 24 of them -- 16 men and 8 women -- were chosen in a modified lottery that insured a group representative of the class as a whole.

New Pathway student Douglas Bell said he chose the program because "I just knew I wasn't satisfied with the way I was learning as an undergraduate . . . So I thought any change would be good."

"We made a tradeoff, for us it's taking a chance being in this program," said classmate Wanda Barfield. "Some other people said, 'I like the security of lectures, 'camels' [typed lecture notes handed out to students under the old curriculum] . . . ' "

Two major themes distinguish the New Pathway from the old. One is early and ongoing exposure to patients. The other is early and ongoing exposure to computers.

Each Wednesday afternoon, New Pathway students meet with practicing physicians assigned as their tutors for their entire four years. They learn to conduct a medical interview, see patients and study the psychology of patient-doctor interactions. Students under the old curriculum do not see patients until midway through their second year.

Dr. Susan Block, who helped design the patient-doctor section of the program, said it includes discussion of cases that "highlight how a psychosocial understanding, and an understanding of disease prevention . . . will affect their care of patients."

Computer fluency is also emphasized. Each New Pathway student and faculty member was issued a personal computer, funded by a $5 million grant from Hewlett Packard. They use computers to ask each other questions, to search the medical literature and to study self-teaching programs on cell biology, cardiac physiology and other topics developed under the direction of Dr. Octo Barnett, the school's director of information processing.

A major goal of the small classes and permanent tutors is to provide mentors, said program director Moore. "It's our hunch that a lot of the personal characteristics of physicians are developed out of role models," he said. "You can't teach honesty, sensitivity . . . You have to see it and feel it."

Working in small groups also fosters cooperative learning. "It's the independent, cut-throat, 'I'm-in-it-for-myself' attitude that we'd like to squash out," he said.

This cooperation helps ease the competitiveness usually experienced by first-year medical students. "Whatever stress I feel, I only feel from myself," said Nancy Fishbein. "There are not enough hours in the day to learn what I would like to learn. From other people, all I feel is support."Moore said his dream is to extend the New Pathway philosophy into residency training. Plans are under way, Tosteson said, to "completely redesign" the third and fourth years -- now spent almost exclusively in hospital work -- to include continued teaching of science and increased exposure to outpatient care.

Adoption of the New Pathway as Harvard's standard curriculum will require its approval by the entire faculty, some of whom prefer the lecture method because it leaves more time for research, Goodenough said. When the faculty might vote is not known.

Some critics of the program fear it will make medical education more expensive. It currently costs the medical school $40,000 a year to educate each student. Tosteson was optimistic that, once in place, the program would be no more costly in dollars or faculty time than the old curriculum.

New Pathway student Barfield said she finds the program an accurate reflection of her future as a doctor. "You don't always know what you need to know," she said. "It's the same when a patient comes in the hospital . . . That's something you have to be comfortable with."