To get information about THACO, AC and other AD&D related stuff read the "walkthrough" by Dan Simpson. You can get it from www.gamefaqs.com (check the Baldur's Gate section).

THAC0 = To Hit Armor Class Zero

It is a factor that in the D&D and AD&D system (which the Baldur's Gate series uses) helps define your ability to hit an opponent. It is the number that you, an NPC, or an opponent needs to attack an Armor Class zero target successfully. Your THAC0 depends on your class, level, and improves as you attain higher levels.

Basically, whenever you attack in BG2, the game calculates a number based on your THAC0 and your target's armor class, and then generates a number from 1-20. Your target's AC is subtracted from your THAC0 and this number becomes the "to hit" number. If the number generated is equal to, or greater than your "to hit" number, your attack succeeds; if not, it fails. Generally speaking, the lower your THAC0, the better.

Quick example (taken from the manual):

A 3rd-level fighter with a THAC0 of 18 attacks a hobgoblin with an AC of 5. The hobgoblin's AC is subtracted from the fighter's THAC0, resulting in a "to hit" number of 13. In order for that fighter to successfully attack the hobgoblin, the number generated by the game for that attack would have to equal 13 or higher.

Hope that helps. =)

Thanks a lot erydian it help a lot but i want to just another thing what is the lowest thaco number we can get and how??? i finished ice wind dale i think you wiil do it wiyh your tools?? am i right or do you make something special while you are creating your character? thanks again

<blockquote>quote:</font><hr>Originally posted by HASSAN:
Thanks a lot erydian it help a lot but i want to just another thing what is the lowest thaco number we can get and how??? i finished ice wind dale i think you wiil do it wiyh your tools?? am i right or do you make something special while you are creating your character? thanks again<hr></blockquote>


have you got a bg2 manual?

and in order to get a lower thac0 some items lower your thaco further.

Regardless of THAC0, rolls of one always miss and rolls of 20 always hit. Right?

<blockquote>quote:</font><hr>Originally posted by Sir Kenyth:
Regardless of THAC0, rolls of one always miss and rolls of 20 always hit. Right?<hr></blockquote>

With the exception of creatures needing certain weapons to hit them (ie a werewolf needs a +1 weapon to hurt it and you're swinging a normal long sword) yes, in the game a 20 also counts as a critical hit and doubles the amount of damage you do (I don't recall whether it doubles all damage or just the base damage- weapon roll before adding in magical plusses, strength bonuses, etc...) unless they are wearing a helmet, in which case the game will tell you that a crit has been averted by the helm.

exactly. you can have a thaco of 25, against a person who's ac is -25, roll a 20, and nail him for a critical!! however, if you have a thaco of -25, and are going against someone who's ac is 25, and you roll a one, you miss! i use these numbers just to show that yes indeed, no matter WHAT thaco and ac are involved that a one ALWAYS misses, and a 20 ALWAYS hits. now thats not saying you will do any damage though..........