IRS Topic 419 - Gambling Income and Expenses:
http://www.irs.gov/taxtopics/tc419.html
"However, the amount of losses you deduct may not be more than the amount of gambling income you have reported on your return. It is important to keep an accurate diary or similar record of your gambling winnings and losses. To deduct your losses, you must be able to provide receipts, tickets, statements or other records that show the amount of both your winnings and losses."
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I don't see anything about expenses, so I wonder if you could deduct expenses over and above gambling winnings IF you establish your BJ playing as a business. The hard part if audited might be convincing the IRS you had a reasonable expectation of making a profit. Otherwise they might decide it's a hobby, not a business .. something I've heard they do with people who have hobby-like businesses that show a loss year after year.