In yet another sign that the bulls are back, Ameritrade (NASDAQ:AMTD) raised its earnings guidance on Friday morning, citing a record month of trades in January. Investors took this as a "buy" signal, sending shares of Ameritrade nearly 5% higher during the day's trading session and bidding up rivals' shares as well.

For a deep winter month, January wasn't bleak at all for Ameritrade. The company said that its average daily volume of trades was 254,000, much higher than the previous record of 182,000 trades per day back in September of last year. Also, Jan. 20 was a red-letter day, with a whopping 326,000 trades.

Ameritrade expects fiscal second-quarter earnings of $0.13 to $0.19 to per share. It sees fiscal 2004 earnings to come in at $0.53 to $0.79 per share (previously, the company's low end of 2004 guidance was $0.49 a share, a figure that had already been increased once).

Other beneficiaries of the good news included E*Trade (NYSE:ET) and Motley Fool Stock Advisor pick Charles Schwab (NYSE:SCH). Toronto-Dominion (NYSE:TD) -- which owns TD Waterhouse, a brokerage that was recently in the news after aborted merger discussions with E*Trade -- also enjoyed a stock price increase.

The idea that individual investors have been returning to the stock market again after several down years isn't new, and in late January, E*Trade enjoyed similar bullish signs -- as did Ameritrade when it reported first-quarter earnings recently.

As long as the current optimism continues, it stands to reason that the discount brokerages will continue reporting upbeat numbers. However, any hiccups in the recovering economy -- or continued investor fears of being burned by another bubble, for that matter-- could result in a reversal of fortune.

Are you thinking about getting into the stock market? Shopping for a new discount broker? The Motley Fool's Broker Center contains many valuable resources for individual investors. You can talk things out with other Fools on the Discount Broker discussion board.

Alyce Lomax welcomes your feedback via email.