Dr. Ralph D. Lillie, 83, former head of pathology at the National Institutes of Health and a pioneer in histochemistry, died Friday in New Orleans.

Professor emeritus of pathology at the Louisiana State University Medical School, he had been working actively in research until suffering a stroke in July.

Dr. Lillie joined the staff of the medical school in 1960 after retiring here as a medical director of the U. S. Public Health Service's commissioned officer corps. At the time, he was chief of the laboratory of pathology and histochemistry of the National Institute of Arthritis and Metabolic Diseases.

He joined the USPHS in 1920 on the West Coast and was commissioned a year later. He came to Washington in 1925 to work in the old Hygienic Laboratory which became the National Institutes of Health five years later.

Dr. Lillie served as chief of the NIH pathology laboratory, director of the division of pathology and pharmacology and chief of the pathology department of the clinical center during his long tenure at NIH.

In 1947 he published a book, "Histopathological Technic," and revised the third edition in 1965, adding "and Practical Histochemistry" to the title and contents. Histochemistry is the study of chemical components of cells through the use of chemically specific staining reagents.

Dr. Lillie was editor-in-chief of the Journal of Histochemistry and Cytochemistry from 1952 to 1964. He was the author of numerous publications in his field.

He was born in Cucamonga, Calif., and grew up in San Francisco and pmonterey. He graduated from Stanford University, where he was elected to Phi Beta Kappa. He also earned his medical degree at Stanford.

He was an Army veteran of World War I.

Dr. Lillie was a fellow of the American Institute of Pathology and a past president of the International Academy of Pathology, the Histochemistry Society and the Biological Stain Commission. He was a member of the American Association of Pathologists and Bacteriologists. He had been honored with a Sustaining Members Award by the Association of Military Surgeons.

He retired to the title of professor emeritus at LSU eight years ago but continued to teach.

He is survived by his wife, Ethel A., whom he married 59 years ago, who is of the home; seven children, Margaret A. Lusk of Annapolis, Susan Jane Lillie of Washington, Mary M. Wallace of Wellsboro, Pa., Ralph D. Jr., of Hot Springs, S. D., William A., of Sunnyvale, Calif., Andrew T., of Bethesda, and Ruth Turney, of Reno, Nev., 16 grandchildren and one great-grandchild.