Thirteen years ago, Eduard Shevardnadze, the Soviet Union's new foreign minister, was given the seemingly thankless job of cleaning out corruption in the his native republic of Georgia.

From all accounts, it was Herculean, like tackling the Augean stables. "Is there nothing that is not for sale here?" Shevardnadze was reported as asking at a Communist Party meeting in 1972 after becoming the republic's first secretary. "If there is, I cannot think of it."

With a tough approach, a modest manner and a flair for public relations, Shevardnadze (pronounced Shev-ard-NAHD-zee) launched his cleanup campaign: hundreds of corrupt officials were retired, some put in prison, notorious black-market rings were uprooted and stolen loot returned to public coffers.

It was on the basis of these successes that Shevardnadze went on to develop a reputation for implementing agricultural reforms and for experimenting in uses of public opinion polling.

In 1978, he became a candidate member of the Politburo. But when he was not promoted to full membership at the last two party plenums, some observers here began to see him as a local success story without a future in the capital.

But at 57, the former Georgian interior minister, unpretentious, even unconventional, whose wife used to take the bus to work at a time when families of Georgian officials lived in palatial villas and rode in chauffeured limousines, has been named to represent the Soviet Union in foreign affairs.

Shevardnadze, little known outside Georgia, is the newest man on Soviet leader Mikhail Gorbachev's team. He replaces Andrei Gromyko, the world's elder foreign minister, who after 28 years in the post was named president today.

In choosing Shevardnadze, Gorbachev settled on someone who in foreign affairs is virtually a blank slate. Shevardnadze has traveled to nine countries since 1960, including Algeria, Austria, Brazil, India and Portugal in the West. But until today, no one in Moscow's diplomatic community had him pegged for a foreign policy role, let alone the top job in the Foreign Ministry's Stalinist skyscraper.

Some diplomats speculated that Gorbachev may have chosen a Politburo member from one of the Soviet minority populations as a signal that could be well received in the Third World. They also noted that Shevardnadze hosted a conference on African and Asian solidarity in the Georgian capital of Tbilisi last October and attended a similar conference in Algeria earlier in the year, establishing contacts in parts of the world where Gorbachev is interested in winning friends.

Both leaders came up through the Komsomol, or Young Communist League, and may well have first met each other as Komsomol officers in the late 1950s. Shevardnadze's experiments, begun in 1974, with agricultural production units -- which brought farms and agricultural industry into single administrative units -- later became a special interest of Gorbachev, who in 1978 became party secretary in charge of agriculture.

In choosing someone with little foreign policy background, Gorbachev is assured of keeping the upper hand in Soviet external affairs, while at the same time still benefiting from the advice of Gromyko.

Shevardnadze was named yesterday to full Politburo membership, replacing Gorbachev's old rival, Grigori Romanov. Now, his accession to Gromyko's job has shaken many assumptions here. After watching Gromyko for 28 years, both Soviets and foreigners found it difficult to grasp the idea of someone taking his place.

At the Supreme Soviet, or legislature, where the change was announced today, normally reserved delegates turned to whisper to one another. The shift from the stony-faced member of the old guard to a robust, relaxed manager was one of the more dramatic since Gorbachev took power in March.

"You only have to watch him," said one western diplomat. "He is not sour, he has a jovial face and he would seem not averse to enjoying life. He has what one might call the discreet charm of a Transcaucasian home secretary."

Shevardnadze's flair has been more apparent in Georgia, a mountainous republic that is one of the country's more romantic regions, populated by a hospitable people. Several times, he has waded into the middle of local crises to make a personal appeal for order: when a hijacked plane landed in Tbilisi, he was at the airport to supervise. When fans at a soccer match between Georgia and Armenia started spilling onto the field, he was reported to have taken the microphone to order people back to their seats.

Shevardnadze also was said to have played a key role in restoring the Georgian language to the republic's constitution after it had been taken out by Moscow.

The use of televsion in his campaigns, and the collection of public opinion data by Georgia's Center for Studying Public Opinion, show an interest unusual here in the tools of modern media. For instance, while attacking corruption in Georgia's universities, Shevardnadze instituted a system of televising oral exams so parents sitting in lobbies could be assured that their children's grades were justly awarded.