From Wikipedia
•Market participants
Market participants
According to the BIS study Triennial Central Bank Survey 2004

•53% of transactions were strictly interdealer (ie interbank);
•33% involved a dealer (ie a bank) and a fund manager or some other non-bank financial institution;
•and only 14% were between a dealer and a non-financial company.
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Banks
The interbank market caters for both the majority of commercial turnover and large amounts of speculative trading every day. A large bank may trade billions of dollars daily. Some of this trading is undertaken on behalf of customers, but much is conducted by proprietary desks, trading for the bank's own account.

Until recently, foreign exchange brokers did large amounts of business, facilitating interbank trading and matching anonymous counterparts for small fees. Today, however, much of this business has moved on to more efficient electronic systems, such as EBS, Reuters Dealing 3000 Matching (D2), the Chicago Mercantile Exchange, Bloomberg and TradeBook(R). The broker squawk box lets traders listen in on ongoing interbank trading and is heard in most trading rooms, but turnover is noticeably smaller than just a few years ago.
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