The director of the Peace Corps will announce a nationwide campaign to double the number of overseas Corps volunteers within five years in a speech here today, according to Peace Corps press officer James C. Flanigan.

Loret M. Ruppe will detail the Leadership for Peace campaign at 4 p.m. in Longfellow 100. The campaign will encourage universities, civic groups, labor and social organizations to provide volunteers to the 26-year-old organization which sends technicians, scientists and laymen to more than 60 developing countries.

And at a press conference tomorrow, the Harvard School of Dental Medicine and the Boston University School of Public Health will formalize programs to send graduate students overseas with the Peace Corps for degree credit.

"We can't do it alone," Flanigan said of the volunteer drive. "We need the help of corporations, universities, unions, minorities, civic groups and other organizations. And we need people with specific skills ... and there's a drastic need for dental health care."

The campaign was spurred by a Congressional mandate two years ago to increase the number of overseas Peace Corps volunteers from its current level of 5200 to 10,000 by 1992.

Congress raised the Peace Corps annual budget by $7 million this year and is expected to add another $10 million next year, said Jana B. Sample, public affairs specialist for the New England Peace Corps. The 1986 budget stood at $130 million.

Both the Harvard and B.U. programs offer volunteers six-month stays overseas. Traditionally, the Peace Corps requires two-year stays, because volunteers need at least six months to learn a language and culture, according to Flanigan.

The Harvard program will be open to fifth-year dental students who have passed professional examinations, while the B.U. program will be made up of masters candidates in public health.

"Sometimes we have to tailor our programs to the enthusiasm we meet," Flanigan said. "So we're trying for the first time to have tours of variable lengths if it can bring in people and specialty skills."