STANFORD, Calif. (AP) _ A Polish boy whose live-saving heart surgery was made possible by $25,000 in donations from about 1,000 people across the country was released Sunday from Stanford University Medical Center.

Piotr Sternik, in critical condition and breathing with the aid of a respirator before surgery to repair a defective heart valve Jan. 25, was in good condition when he left, said Laura Hofstadter, a hospital spokeswoman.

The 6-year-old boy walked out of the hospital on his own and got into a car for the trip to Carmel, 70 miles to the south, where he and his mother, Halina Sternik will stay while the boy is recuperating, according to Peter Wasowski, their host.

The boy, from Gdansk, Poland, had a congenital heart defect that caused much of his blood to bypass his lungs, where blood is reoxygenated.

One of every 4,000 infants worldwide is born with problem, the hospital said in a statement. It said 90 percent who do not get the treatment Piotr received die within a year of birth.

Piotr's father, Michal Sternik, a former activist with the Solidarity trade union, stayed home during the mission to save the boy's life.

The boy's admission to Stanford was delayed briefly when the hospital requested payment of $25,000 in advance. Some 1,000 people around the country chipped in to provide Piotr with the money.

Surgeons grafted a new valve from a donor heart onto Piotr's heart, and patched a hole between the chambers.

Because the Sterniks planned to return to Poland, surgeons used human rather than animal tissue to reduce the danger of rejection, center spokesman Mike Goodkind said.

It may be the end of March before the boy is allowed to return home, Wasowski said.

Before Piotr leaves, Wasowski said, a news conference will be held to let the many people who donated money to save the boy's life know the happy result of their gifts.

''We owe it to those people to let them know how this came out,'' he said.