Being able to read MMs only helps in a few situations. If you're a scalper then it is imperative to understand this. When a MM is at the inside price and is the only market participant it is important to watch his share size and T&S. Rarely do you see prints in T&S match the inside decremented display share size at the same time. My point is if a MM (NITE) is at the inside bid by himself displaying 1,000 shares at 15.05 and you see prints ripping continuously at 15.05 then chances are good that NITE had and has many more shares that he wants to accumulate behind that 1,000 display size but doesn't want to tip his hand and show the entire size. Along those lines, he might display 1,000 and execute and decrement down to a 100 then auto refresh back to 1,000 and continue that until he accumulates his total position. When you see this don't go against the MM...in this example he is buying and this is called "soaking up the bid"....this is agreat short-term indicator for scalping. There will be a few times when the MM soaks the bid or ask then the market moves against him. That is when the MM is on the WRONG side of the trade and losses his pants unless he has a lot of backing and can wait it out. It's also important to realize which MMs are soaking...if you see Goldman (GSCO), Merrill (MSCO) Nite Trimark (NITE), Herzog (HRZG), ect; the big guys...you might want to follow their lead. I don't give as much weight to the smaller MMs since I know they won't attempt to control the market unless it has low volume. If one is soaking the bid at 17.50 for a lot of shares, you'll also see them post an ask size, usually small, because they have to since they make a market in the stock...don't think that's their exit point on the block they just soaked up.