The remains of two U.S. soldiers missing during the Vietnam War were also returned at a ceremony at the Vientiane airport.
"I am pleased to hand over to you the remains ... Without the cooperation of the local people they would not have been able to find the remains," Laotian Vice Minister of Foreign Affairs Phongsavath Boupha said in a speech.
He called the ceremony "a symbolic victory" in relations between the two countries.
The likely remains of Charles Dean and Australian Neil Sharman were exhumed earlier this month in central Laos following a tip by a Laotian villager. The other two sets of remains were excavated from other sites in northeastern Laos.
"Formal confirmation of who the remains are won't be made until the remains actually are examined in the forensic laboratories in Honolulu," U.S. Embassy spokesman James Warren told CBS Radio News.
Howard Dean, who is seeking the Democratic nomination in next year's presidential election, said last week his family is convinced the remains belong to his brother. He said they include bones, a sock, a pair of shoes and a bracelet his brother had with him.
"I understand that family members from the Dean family and other families will be in Honolulu for an arrival ceremony when the remains arrive," said Warren.
The four sets of remains were transferred to aluminum caskets brought by a U.S. military C-130 cargo plane. An honor guard draped one casket in an Australian flag and the other three in U.S. flags before loading them on the plane.
"Today marks another special day for repatriation of remains from the Indochina war," said U.S. Ambassador to Laos Douglas A. Hartwick.
"This cooperation is a key element in bilateral relations," he said.
Charles Dean disappeared in 1974, when the 24-year-old University of North Carolina graduate was traveling through Southeast Asia with Sharman. Both are believed to have been imprisoned and killed by communist insurgents who took control of Laos in 1975.
An investigation into their disappearance began in 1991, and the first of two joint U.S.-Laotian excavation teams began digging in August.
A Laotian villager led the investigators to a site near a boulder in a rice paddy near the town of Lakxao, about 25 miles west of the Vietnamese border in Bolikhamxai province.
The site was pocked with bomb craters and had to be cleared of Vietnam War-era ordnance, excavation team leader Elizabeth Martinson said Sunday. She would not give any other information about the villager or the remains.
"Since 1992 the remains of 182 Americans have been recovered in Laos" since 1992, said Warren. "There are still 387 Americans still unaccounted for" from the Vietnam War era
Phongsavath, the Laotian minister, expressed the hope that the handover would persuade the U.S. Congress to establish normal trade relations with Laos.
The United States has diplomatic ties but no trade links with Laos because of concerns about the communist government's human rights record.
"We hope that this will help the American people and the Congress to understand that we have also shown our goodwill to cooperate" on the issue of missing Americans, Phongsavath said.