Robert Harold Parrott, 76, the pediatrician and virology researcher under whose direction Children's Hospital was transformed from a local pediatric facility into a national medical center for young people, died of a stroke Dec. 26 at his home in Highland.

During the three decades in which Dr. Parrott oversaw hospital operations, Children's became an international force in the care of children and research into pediatric diseases.

It opened its own research laboratories and began programs for abused children that became national models. At the same time, it fulfilled a pledge that children without resources would not be turned away. About a third of its outpatients during Dr. Parrott's time were unable to pay, and about a fifth of those who stayed for treatment were also indigent.

Children's never received direct government operating funds. Like most unaffiliated children's medical institutions in this country, it depends on community philanthropy and struggles with a persistent operating deficit.

Dr. Parrott, who served his residency at the old facility at 13th and V streets NW, returned in 1956 to become its first full-time staff physician. Young patients were generally treated in the facility by their private doctors.

It was a crumbling building, the descendant of a foundling home that had modest beginnings in the era after the Civil War.

Washington's middle class was moving to the suburbs, leaving behind socially and economically disadvantaged families. Children's hospitals, faced with competition from general hospitals, were on the verge of bankruptcy all over the country.

In 1977, after more than a decade of planning and fund-raising by Dr. Parrott and others, and with a matching construction grant approved by Congress, Children's Hospital moved to an $80 million, state-of-the-art facility at 111 Michigan Ave. NW.

By the time Dr. Parrott retired in 1985 as senior vice president of academic affairs, the medical center was employing more than 250 full-time physicians and researchers. It continues as the pediatric training facility for George Washington University, for which Dr. Parrott also served as chairman of child health and development.

Internationally known for his research into viruses that cause severe respiratory diseases in children, Dr. Parrott was instrumental in setting up the hospital's virus lab shortly after he was named physician in chief. He continued to have a hand in research at the facility throughout his career, and he was involved in pediatric AIDS research there up until this fall. He wrote or contributed to about 150 articles for scientific journals and textbooks.

Dr. Parrott was a native of New York and a graduate of Fordham University. He received his medical degree from Georgetown University and did his internship at the Hospital of St. Raphael in New Haven, Conn.

As a young resident at Children's, he received the first fellowship of the new Children's Hospital Research Foundation, and he continued his work in viruses that affect children while serving in the Public Health Service at the National Institutes of Health.

Dr. Parrott's interest in medical research began early. As a young man, before antibiotics were in use, he suffered from a bone infection that left him with a limp and dependent on crutches.

Calm and unflapable, Dr. Parrott was active on the wards of Children's for much of his time there, despite the pressures of fund-raising and his own deep interest in research.

"His gift was to hire people he thought had great promise and give them a tremendous amount of freedom to explore their fields," said Peter R. Holbrook, the current chief medical officer who had directed the intensive care unit for 20 years.

Under Dr. Parrott's leadership, Children's also "developed one of the most comprehensive child-abuse facilities in the country and the most comprehensive sex-abuse facility in the country," Holbrook said.

Away from the hospital, Dr. Parrott's interests included power boating on the Chesapeake Bay. He was a member of St. Jane de Chantal Catholic Church in Bethesda before moving in 1990 to Highland, where he belonged to St. Louis Catholic Church.

His wife, Paula Parrott, a former nurse, died in 1993, and a son, Timothy Parrott, was killed in a car crash in 1977.

Survivors include his children, Edward Parrott of Washington, Maureen McGrew of Burtonsville, Theresa Parrott of Bethesda, Christopher Parrott of Rockville and Daniel Parrott of Vera Cruz, Mexico; a sister; and seven grandchildren.