Check the Currency Risk. Then Multiply by 100.

CURRENCY trading isn't just for money center banks, multinational corporations and hedge funds anymore.

Online traders with a hankering for high-risk speculation have embraced the vast and volatile forex market, as the global foreign exchange market is called.

Getting started is a snap. Investors can open an account over the Internet with a deposit of just a few hundred dollars. Downloading a trading platform takes minutes. Then they can start wagering in real time on which currencies are headed up or down. Because trading occurs in Tokyo, London, New York and other world financial centers, it's possible to speculate day and night from Sunday afternoon to Friday afternoon Eastern Standard Time.

But watch out. The leverage on a standard trade is a breathtaking 100 to 1. That means a customer who puts up ,000 controls 100 times that, or 0,000. Trading primarily with borrowed money magnifies even minuscule moves of one currency against another into sudden big gains or huge losses. A 100 percent gain on a position, or a total wipeout, can take place in a few minutes.

For example, a one-cent change in how many dollars it takes to buy a euro - say, to .22 from .21 - amounts to an actual price shift of less than 1 percent. But in a spot forex trade, when 100-to-1 leverage is used, the same slim move is multiplied a hundredfold. So there's a increase for each staked by traders on the euro's climb, and an equivalent drop for those expecting the dollar to go higher.

Of course, profits and losses are not realized until a position is closed out. But investors who leverage themselves to the hilt in pursuit of quick outsize returns often find that they are rapidly burning up the capital in their accounts when a few trades go sour.

Firms provide mechanisms to dial down the leverage to, say, 10 to 1, reducing exposure to risk. But leverage still makes this one of the most hazardous markets for the average investor.

"Currencies should be and are becoming an integral part of a well-diversified portfolio," said Marla Miller, chief operating officer of the MG Financial Group, one of the first firms to offer foreign exchange trading for individual investors. "However, they are appropriate only for investors who can assume the risk of losing everything."

Currency trading isn't merely risky. It's also complex, from the rudiments of trading techniques to understanding the supply-and-demand factors that lie behind the constant shifts in relative currency values.

To follow the fundamentals of the forex market, it helps to be a maven of global macroeconomics and a fiend for geopolitics. Investors who are trading the dollar in relationship to the euro would be wise to parse every nuance of the comments of Alan Greenspan, the Federal Reserve Board chairman, about interest rate policy, as well as the deliberations of the European Central Bank and the words of its president, Jean-Claude Trichet.

Big-picture issues can preoccupy the currency markets. Today, the questions include these: How much has the euro been wounded by decisive votes in France and the Netherlands rejecting the European Union's proposed constitution? Will China effectively revalue the yuan, and by how much? And would such action by China set off a cataclysmic decline in the dollar?

Technical traders, who ignore such fundamental issues, instead take positions by analyzing chart patterns with arcane mathematical tools like Fibonacci retracements and Ichimoku clouds. Such traders have adapted readily to the foreign exchange market because currencies tend to move in long-term trends.

The interest of many technical traders was galvanized by the three-year climb of the euro against the dollar, from around 85 cents at the start of 2002 to just above .35 at the end of 2004 - a climb of around 60 percent. In this highly geared market, a ,000 position at the start, leveraged at 100 to 1, would have become ,000 in three years.

This year, of course, the dollar has changed course, rallying sharply against most major currencies, including the British pound and the Japanese yen but especially against the swooning euro. (Early last week, the euro fell to just above .20; it approached .23 on Friday.) Traders are divided over whether the dollar's rebound is simply a respite in a more prolonged drop or the start of a major reversal.