WASHINGTON (AP) _ Ervin S. Duggan, president of the Public Broadcasting Service, resigned today after shepherding PBS through more than five years of ``mission-oriented'' growth.

``PBS has been significantly strengthened under Ervin Duggan's leadership,'' PBS Board Chairman Colin G. Campbell said in a statement. ``His efforts have earned the appreciation of our colleagues in public broadcasting and of a citizenry that recognizes and depends on the excellence he has championed.''

Duggan said he had fulfilled his objectives for the Alexandria, Va.-based association of public television stations during his 5 1/2-year tenure. ``A strategy to create greater financial security and enduring value for PBS and its member stations is now in place,'' Duggan said.

``I have relished serving as a public champion of PBS's unique mission of education, culture and citizenship,'' he added.

Under Duggan's reign, PBS increased revenues 70 percent _ from $182 million in 1995 to a projected $309 million in 2000. PBS, which serves 100 million people weekly, also took on new ventures, including PBS Online and the PBS Kids channel.

However, Duggan is not retiring, said PBS spokesman Tom Epstein.

``He's going to explore what else is out there,'' Epstein said. ``He felt he couldn't look for something new while he was still full time with PBS.''

PBS board member John F. Swope will serve as interim chief executive when Duggan leaves Oct. 31.