Playing vanilla BG1.

I've read up about THAC0 and class levels, but still can't work out if increased strength lowers (improves) THAC0 for a given character. In the 3rd edition rules increased strength makes it easier to hit in melee, and increased dexterity makes it easier to hit using ranged weapons so I've designed my toons with this in mind.

I looked at the 3rd edition mod on the Beamdog site to try and work this out but I'm still confused. Every now and then someone says "NPC x is a better archer because they have higher dexterity" but without any clarity on WHY!

Take a look at this:

https://www.gamefaqs.com/pc/75251-baldurs-gate/faqs/8566

Yes. Strength affects THAC0, damage, carry weight and door/lock bashing.

Look here.

This rule only applies at character creation. Once the game has started, the rule isn't enforced any further. In particular, I note:

* Dual classing a character will not change whether the character has exceptional strength. A fighter who changes into a mage will keep her exceptional strength, even before regaining her fighting abilities. Dual classing from mage to fighter will not allow the character to gain exceptional Strength.

* The Strength spell sets a character's Strength to 18 and increases exceptional strength by 50. Hence, one casting gives a character 18/50 Strength, and a second casting 18/00 Strength. (If a character has at least 18/01 Strength naturally, but less than 19, the character will have more than 18/50 Strength, but a character with 19 or more Strength will have it lowered to 18/50 (note that this can be used offensively to weaken giants and other high Strength enemies).)

* Strength of One will set Strength to 18/75, even if it's higher. (Note that this can't be use offensively (unless you charm/dominate the enemy first) because it only affects allies.)

* Polymorph and Shapechange effects can cause a character to gain or lose exceptional Strength. It will also boost a plain 18 to 19. A score of 19 is better than any amount of exceptional 18/xx Strength (except for the counter-intuitive interaction with the Strength spell I mentioned above). Two easy ways to boost Strength to 19 or higher are to use Draw Upon Holy Might or to be a Half-Orc.

By the way, 19 is +3/+7, which is *far* better than 18's +1/+2, so you should try to get that 19th point if you can and don't have a good exceptional Strength value.

(Really, the exceptional Strength rule makes things far more complicated than they ought to be; I think you can see why 3e nixed this rule.)

PIHwiki: Strength.

Thanks all for the helpful responses. The link to the phwiki laid it all out compactly.