SECRET SWAPS. Icon for your Nikon? Samovar for your Sony?

SERGEI pulls off to the side of Nevsky Prospect and checks his Rolex for the time. His head is lost in a fog of rhythm, as Grace Jones blares from his Pioneer car stereo: ``I'm not perfect, but I'm perfect for you.'' Sergei's friend Sasha is five minutes late for lunch. Peering through the windshield, Sergei spots two down-jacketed figures. The unzipped jacket of one boy exposes his L.L. Bean sweater. Americans, Sergei notes. Those coats must cost a lot in the West and would probably bring in five times more here. He hops out of his car. Why not talk to two young tourists?

Sergei (not his real name), one of countless black market dealers throughout the Soviet Union, approaches his trade with the assured air of a Wall Street stockbroker. He shies away from the riskier game of money exchange, where dollars go for as much as five rubles, rather than the official rate of 0.64 rubles. (The government jealously guards the flow of foreign currency, which it needs for foreign trade.) Instead, Sergei exchanges things - clothing, cassette tapes and players, even aspirin - for the standard Russian treasures: icons, Soviet flags, and black lacquer boxes.

Sergei approaches the two young men and begins speaking English. His own self-taught version mixes phrases from Western movies and rock music with a good measure of American slang. The college men are impressed: for them this is a rare opportunity to meet a ``real'' Russian. They agree to dinner that evening - 6o'clock in the park by their hotel.

This is not an isolated incident for Sergei since he is usually in pursuit of foreigners. He says he thrives on conversations about politics and Western music - topics he can't discuss with most of his compatriots. ``You know better than I do the level of discontent in this country,'' he tells a visiting foreigner. ``I don't like to talk about it with other Russians.''

But he also, of course, thrives on the foreigners' goods. For the average Soviet citizen it's hard to make ends meet. Even a pair of inferior-quality shoes can cost one-third of a typical monthly salary. This situation often drives Soviets to find alternate sources of income and consumer goods. In a good week, Sergei can earn 400 rubles (about $625) - an amount it takes an average Soviet more than two months to earn.

``Everyone in the Soviet Union is involved in the black market,'' Sergei says. And many instances support this assertion: A priest listens to Andrew Lloyd Webber's ``Requiem'' on a Sony cassette player; a university professor pads around in Nike running shoes; an author reads the English version of Boris Pasternak's outlawed ``Dr. Zhivago.'' Although some goods are received from foreign friends or relatives living abroad, most are acquired through the black market.

Insider trading

Traders obtain their goods in a mysterious fashion, sometimes from another black marketeer who has access to a supply of lacquer boxes for sale for rubles. Less well-connected marketeers rely on fur hats available in Soviet stores and old family icons to attract trade.

Some marketeers have regular channels to the West through tourists who come regularly and know precisely what to bring. And unlike Sergei, many marketeers trade for American dollars, which they can use to buy goods in a beryozka - a foreign-currency store. Although it is illegal for Soviets to have foreign currency, many marketeers find foreigners to do the buying for them.

Sergei lives by his own set of rules: He never goes into a beryozka. He never speaks openly in front of any Soviet he can't absolutely trust. He's never specific on the telephone about friends or meeting places. When talking in his apartment about anything significant, he breaks the circuit on his phone by placing a paper clip in the dialer (to foul up any listening device). Meetings with anyone he doesn't know take place in a car. Employed by the KGB

The authorities do a significant amount of back-turning to the black market, which is too vast to keep in check. Many marketeers end up in the employ of the KGB secret police, where they learn to keep an eye on one another and on foreigners.

Sergei's closest friends know he wants to leave the Soviet Union. Life here is a dead end, he says: ``I see myself coming to a very bad end here - narcotics or something.''

But when asked why he doesn't do something ``constructive,'' he counters passionately, ``I cannot create anything here. I cannot take the initiative. This government won't allow me to. Yes ... they speak of perestroika [economic reconstruction] and the new economics of individual initiative. But I am sure that if I put my name on the list of people who wanted to open a private enterprise, I would get a different answer.''

Soviets who criticize the black market say that traders' fascination with the West causes them to become Westernized and to sever their ties with the motherland. They say traders misrepresent their homeland by giving foreigners the impression that all Soviets are disillusioned with the goals of communism.

Sergei says the term ``black marketeer'' leaves a bitter taste in his mouth and gives many Westerners the wrong impression. ``Naive Americans come here and think I'm a criminal. They're scared to talk to me. I don't sell drugs. I just trade. You know ... I help you, you help me.''

Sergei does have a job, as required by the government. He works a 12-hour shift three days a week as a boiler man in a factory. But he says he's neither challenged nor fulfilled by his job. Why bother to go to work, he says, especially when your boss will overlook your absence in exchange for the occasional use of your VCR? Modest living

The VCR blinking silently in one corner of Sergei's small, three-room apartment - which he shares with his sister and mother - is his only sign of affluence. Yet small clues betray his involvement in the black market: an American flag, a photograph of his idol, Jack Nicholson, and hundreds of buttons announcing in English everything from ``Reagan in '84'' to ``I love you.''

Compared with many black marketeers, who keep their apartments stocked with boxes, fur hats, champagne, caviar, and art books, Sergei's apartment is barren. One starts to think that maybe his main interest is truly not just money, but meeting foreigners.

Sean, a college student from Washington, D.C., was approached on the street by Sergei while on a tour. After some conversation, the Americans were invited to a party. There, Sean became fascinated with the trader.

``In one room I was talking with the host, who aided dissidents - he was telling me all about [Andrei] Sakharov. And in the other, Sergei had his show going - he literally had 12 people just watching and listening to him. He was going on with a social commentary, running up and down the room, his arms flailing. He was fascinating.''

But the party ended bitterly when some of the Russians began asking for dollars and belt buckles to do a little business.

``It really made you feel like the whole thing had been a ruse,'' Sean explained. ``But Sergei didn't say anything. He just sat back and watched.''