RANKFURT, Jan. 23 — The SuperBowl bowling alley here warns customers before they even get their shoes: it will accept payment only in euros, not in German marks.

"It is too much trouble," the manager said. "It is difficult to keep two separate cash drawers and difficult to make change. So we decided, right from the beginning, that we would only accept euros."

Three weeks after euro notes and coins hit the streets in 12 European countries, the new currency has nearly vanquished the rainbow of old national denominations. The changeover has been so fast and generally so smooth that it has almost ceased to be a topic of discussion.

The European Central Bank estimates that more than 95 percent of all cash transactions in the euro nations are now in the new currency. As of Friday, more than 8.1 billion euro notes, worth nearly $200 billion, had entered circulation. Though the old money can still be used until the end of February in most countries, it has all but disappeared in daily business.

Many taxi drivers and newspaper vendors here in Frankfurt say they no longer want marks. Aldi's, one of Germany's biggest discount grocery chains will accept marks but posts prices only in euros. In France, Printemps supermarkets and department stores like Galeries Lafayette accept only euros at most counters, and buyers with francs are escorted to separate cash registers.

The story is much the same elsewhere. Even in Italy, which suffered from organizational problems in the first two weeks of this month, euros have nearly replaced lire. The most common complaint among Italians is about the new one-cent and two- cent coins, which have annoyed people who are used to paying mainly with paper money.

The introduction of euro notes and coins was described, by government officials as well as the news media, as one of the greatest peacetime logistical challenges that Europe had ever confronted. It required the printing and minting of 15 billion notes and 50 billion coins, the latter bearing the stamp of the country where it was minted.

Yet today the changeover is essentially accomplished.

"The boring thing about the euro is that everything is working so well," said Albrecht von Truschsess, a spokesman for Metro A.G., the huge German retailer that owns supermarkets, department stores and specialty shops across much of Europe.

In Spain, government officials were quietly worried that many people would be reluctant to convert their pesetas to euros because they would be afraid to divulge income they had not paid taxes on.

But the government solved that problem by letting people change as much as 2.5 million pesetas, about $13,200, without having to present a bank with any identification.

Italy had the most serious problems. Banks there were much slower than elsewhere to load cash machines with euros. Post offices, where many Italians pay their utility bills and receive pension payments, nearly ground to a halt as clerks struggled to handle bills and checks written in lire.

Many post offices there still have long lines. But most of the cash machines were converted to euros two weeks ago, and store customers have switched over to euro payments almost as quickly as in other countries.

Italians are grumbling about other aspects of the euro. Some waiters complain that their tips have become smaller, and a priest near Naples made headlines by complaining that the euro had made parisioners "cheap" in their contributions. The problem, he said, is that Italians routinely gave 1,000-lira notes, worth about 51 cents, and are now tossing in coins worth just a few pennies.

In Finland, the government has already eliminated the little coins but is having second thoughts. The Finnish Parliament passed legislation last year requiring stores to round prices up or down to the nearest five cents. Though the Mint of Finland produced a small number of the coins, the country's central bank did not want to release them.

But the central bank recently reversed itself, apparently because many Finns were attracted by the coins' potential value to collectors.

If there is one area where euro conversion is incomplete, it is vending machines. At one gas station here in Frankfurt, cashiers have to supply customers with one-mark coins to buy coffee. In some countries, many cigarette machines have yet to be converted.