According to research data:
53 % of Forex deals are arranged between dealers or banks;
33% are between a dealer (a bank) and a fund manager or other non-bank financial institutions;
14% involves a dealer and a non-financial company.
Banks
The largest part of Forex market belongs to banks. They cater for both the majority of commercial turnover and large amounts of speculative trading every day. Daily turnover of one large bank may reach billions of dollars. And only the small part of this trading is undertaken on behalf of customers. The rest trading banks  arrange for their own account.
Today, large banks have moved on to electronic systems, such as EBS, Reuters Dealing 3000 Matching (D2), the Chicago Mercantile Exchange, Bloomberg and TradeBook(R). This transition reduced foreign exchange brokers’ profit, as they did business, facilitating interbank trading and matching anonymous counterparts for small fees.
Commercial companies
Commercial companies that seek foreign exchange to pay for goods or services are also an important part of the Forex market. Comparing with banks or speculators, commercial companies trade fairly small amount. Besides their trades usually have little short term impact on currency's exchange rates. But sometimes multinational companies can have unpredictable impact on market rates. Especially when market participants don't know about very large positions, covered due to little known exposures. Central banks
National central banks are one of the most important participants of foreign exchange market. Their purpose is to control the money supply, inflation and interest rates. Usually they have official or unofficial target rates for their currencies. Use their substantial foreign exchange reserves as a stabilization market tool. One of the best stabilization strategies, used by central banks, is to buy while the exchange rate is the lowest and to sell when the rate is high. In such a way central banks may get a good profit. Nevertheless, central banks are more protected than other market participants, as they don't go bankrupt if they make large losses. At the same time there is no convincing evidence that central banks do make a profit trading. Currency may be stabilized because of even the mere expectation or rumor of central bank intervention. In countries with a dirty float currency regime, aggressive intervention might be used several times during a year. However central banks' attempts may fail. Because, the combined resources of the Forex market can easily overwhelm any central bank. Investment management firms
Their main activity is managing large accounts on behalf of customers such as pension funds, endowments etc. Investment managers usually use the Forex market to facilitate transactions in foreign securities. Especially if an investment management firm is specialized in foreign equities, it will need to buy and sell foreign currencies in the spot market in order to pay for purchases.
However some investment management firms have speculative specialist currency overlay units. They manage client's currency exposures with the aim of generating profits as well as limiting risk. But the number of this type of investment management firms is comparatively small.
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