Dr. Leonard W. Cronkhite will resign as president of the Children's Hospital Medical Center, a Harvard teaching affiliate, effective August 1.

Cronkhite said yesterday he is stepping down because he wants to make "one more major career change--if I don't do it now, it'll be too late." He said he does not have another job yet.

The trustees of the hospital will appoint a search committee to find a replacement, Cronkhite said. He said Harvard will be consulted on the choice, but will have no official voice in the selection process.

Cronkhite said he is "basically a manager" and will now look for a "chief executive's job in academics."

Cronkhite mentioned three items as the most important advances at the hospital since he began there as general director in 1962.

The physical plant of the hospital has been completely rebuilt, and the research effort "has grown enormously, at least coincidentally with my being there," Cronkhite said.

Thirdly, he said he has worked to assure at the hospital "a single level of care without regard to economic status."

Cronkhite said the uniform level of care is important in a children's hospital, because the environment "is part of the treatment. It's not good to isolate children from their own peer groups. They don't have the same hang-ups that adults have."

Students at the Medical School receive training in pediatrics and many doctors at the hospital are Harvard professors.

Both institutions benefit from the arrangement, Cronkhite said. He said Harvard's students receive practical experience at one of the finest pediatries hospitals in the world, and Children's gets "some of the finest talent in the country."

The agreement with Harvard also makes available to the hospital "an enormous amount of research money," Cronkhite said.

Because the Medical School is basically a teaching facility and the hospital is primarily a service institution, the needs and priorities of each do not always correspond, Cronkhite said. But he said that during his 15-year tenure at Children's there has been "a very good dialogue to try and match each institution's needs."