William Friday, executive director of the William R. Kenan Jr. Charitable Trust in Chapel Hill, N.C., will retire June 30, 1999. A national search will be conducted for a successor.

Friday, 78, has headed the $420 million-asset foundation since 1986. Before that, he was president of the University of North Carolina system for 30 years.

Under his leadership, the foundation has launched and supported major education initiatives. Over the past decade, for example, it created Kenan institutes at the University of North Carolina at Chapel Hill, N.C. State University and the N.C. School of the Arts with grants of $20 million each, contributed $20 million to the Kenan-Flagler Business School at UNC-CH and established a Kenan institute at Duke University.

Friday also serves as president of separate funds that support the four Kenan institutes. His successor will fill those posts as well.