Is there any point in increasing your THACO beyond 0. My character is an archer with THACO of -9 (with mods) should I forget about THACO after o?. any help appreciated

Well, you want to lower it to as low as you can obviously. If you had a THACO of -9 and your opponent had an AC of -11 then you need a 2 or better to hit him (though I can't think of any enemy save maybe drow in the underdark who would have THACO that low. In any case if you roll a natural 1 you miss anyway.

A THACO of -9 is pretty damn good BTW.

It helps when you are fighting someone with an AC less than 0.

When you take a swing/shot at someone, the computer makes the following calculation...
attackers THAC0 - defenders AC = lowest needed attack roll on 1d20.

So, if you have a THAC0 of 0, and the defender has an AC of 3, you're going to hit them with out any problem. However, if the defender's AC is under 0, then you risk a small chance of missing. A THAC0 of -9 would probably hit any enemy in the game who isn't protected by some sort of magic or has some other modifiers.

Thank you Memnock(not any or the other names) and Sir Rich for the replies. I didn't know that an npc could have a THACO below 0.
thanks again
Cormac