Character creation starts with the generation of 6 ability scores which determine the type of character class that a player will play. Each ability score is determined by rolling 3d6.

Strength measures your character's muscle and physical power.

You apply your character’s Strength modifier to:

• Melee attack rolls.
• Damage rolls when using a melee weapon or a thrown weapon (including a sling). (Exceptions: Off-hand attacks receive only one-half the character’s Strength bonus, while two-handed attacks receive one and a half times the Strength bonus. A Strength penalty, but not a bonus, applies to attacks made with a bow that is not a composite bow.)
• Climb and Swim checks. These are the skills that have Strength as their key ability.
• Strength checks (for breaking down doors and the like).

Dexterity measures hand-eye coordination, agility, reflexes, and balance.

You apply your character’s Dexterity modifier to:

• Ranged attack rolls, including those for attacks made with bows, crossbows, throwing axes, and other ranged weapons.
• Armor Class (AC), provided that the character can react to the attack.
• Reflex saving throws, for avoiding fireballs and other attacks that you can escape by moving quickly.
• Acrobatics, Escape Artist, Disable Device, Ride, Sleight of Hand, and Stealth checks. These are the skills that have Dexterity as their key ability.

Constitution represents your character's health and stamina. A Constitution bonus increases a character's hit points, so the ability is important for all classes. Some creatures, such as undead and constructs, do not have a Constitution score. Their modifier is +0 for any Constitution-based checks. A character with a Constitution score of 0 is dead.

You apply your character's Constitution modifier to:

• Each roll of a Hit Die (though a penalty can never drop a result below 1—that is, a character always gains at least 1 hit point each time he advances in level).
• Fortitude saving throws, for resisting poison, disease, and similar threats.

If a character's Constitution score changes enough to alter his or her Constitution modifier, the character's hit points also increase or decrease accordingly.

Intelligence determines how well your character learns and reasons. This ability is important for wizards because it affects their spellcasting ability in many ways. Creatures of animal-level instinct have Intelligence scores of 1 or 2. Any creature capable of understanding speech has a score of at least 3. A character with an Intelligence score of 0 is comatose. Some creatures do not possess an Intelligence score. Their modifier is +0 for any Intelligence-based skills or checks.

You apply your character's Intelligence modifier to:

• The number of bonus languages your character knows at the start of the game. These are in addition to any starting racial languages and Common. If you have a penalty, you can still read and speak your racial languages unless your Intelligence is lower than 3.
• The number of skill points gained each level, though your character always gets at least 1 skill point per level.
• Appraise, Craft, Knowledge, Linguistics, and Spellcraft checks.

A wizard gains bonus spells based on his Intelligence score. The minimum Intelligence score needed to cast a wizard spell is 10 + the spell's level.

Wisdom describes a character's willpower, common sense, perception, and intuition. While Intelligence represents one’s ability to analyze information, Wisdom represents being in tune with and aware of one's surroundings. If you want your character to have acute senses, put a high score in Wisdom. Every creature has a Wisdom score. A character with a Wisdom score of 0 is incapable of rational thought and is unconscious.

You apply your character's Wisdom modifier to:

• Will saving throws (for negating the effects of charm person and other spells).
• Heal, Perception, Profession, Sense Motive, and Survival checks.

Mages with a divine spell source get bonus spells based on their Wisdom scores. The minimum Wisdom score needed to cast a spell is 10 + the spell's level.

Charisma measures a character's personality, personal magnetism, ability to lead, and appearance. It is the most important ability for paladins, sorcerers, and bards. It is also important for clerics, since it affects their ability to channel energy. For undead creatures, Charisma is a measure of their unnatural “lifeforce.” Every creature has a Charisma score. A character with a Charisma score of 0 is not able to exert himself in any way and is unconscious.

You apply your character's Charisma modifier to:

• Bluff, Diplomacy, Disguise, Handle Animal, Intimidate, Perform, Use Magic Device, and Wild Empathy checks.
• Checks that represent attempts to influence others.
• Channel energy DCs for characters attempting to harm undead foes.

Mages with an innate spell source gain a number of bonus spells based on their Charisma score. The minimum Charisma score needed to cast a spell is 10 + the spell's level.

Charisma measures a character's force of personality, persuasiveness, personal magnetism, ability to lead, and physical attractiveness. This ability represents actual strength of personality, not merely how one is perceived by others in a social setting.

Charisma is also used to determine the number of people that can be employed by a character.