Mgregor is pretty much correct regarding the daytrading rule. However, it should be pointed out that this trading call occurs in this situation <b>only</b> if you attempt to trade the following day using more buying power than you would have minus the value of the overnight position. So for instance, in a $50,000 account, if you were to take home $25,000 worth of MSFT and sell it the next day, you lose $25,000 worth of buying power for that day in MSFT only. You could still daytrade up to $50,000 worth of MSFT ($25,000 in cash plus margin). However, if you tried to daytrade more than $50,000 worth of MSFT you would get hit with the margin call. You would of course still have your full $100,000 worth of buying power to trade any other stock besides MSFT.