Fallout 2 uses the SPECIAL system for dealing with basic character statistics, which are one of the primary choices made during character creation. Each statistic effects the starting levels of related skills, secondary statistics like hit points and radiation resistance, as well as in-game checks, like being strong enough to pry a door open. Each trait ranges from 1 to 10, and it's been noted that having any trait lower than 3 or 4 can almost cripple a character. For example, an inteligence lower than 4 renders the character mute, cutting off all but the most simple quests. Only players looking for a serious challenge should even consider starting any statistic so low.
Note: Beyond what is noted below, each SPECIAL statistic can be raised by an additional +1 by taking the corrosponding perk, all of which are available at level 12.
Skills: Melee Weapons, Unarmed
Raw physical strength determines the number of hitpoints you recieve, how much you can carry, as well as melee damage. It's important to note that many weapons, especially big guns, have strength requirements. For each point of strength a character is short of the requirement, they suffer a -20% penalty to their chance to hit. Because of this, it is possible to compensate for a lack of strength by having a high enough weapon skill. Throughout the game the player is able to permanently boost their strength by 5, 1 from the red memory module and 4 by wearing a set of advanced power armor (any type), both of which are explained in detail in the items section. Strength is used to determine the starting levels for all characters unarmed and melee skills. A temporary boost of 4 points is possible through the use of 2 doses of the buffout drug, note that this risks addiction and withdrawl.
Skills: First Aid, Doctor, Lockpick, Traps
Perception is the most important statistic for sniper-type characters, as it dertermines how far they can shoot without losing accuracy (along with the weapon type and appropriate combat skill). While sometimes considered secondary, it also influences sequence, meaning when your character gets to take their turn in combat. If a character's perception is extremely low (being less than 3 or 4) it can even cause you to occasionally miss a turn in combat altogether. A secondary, but sometimes important, influence that perception has is where you start encounters from the map; it can spell the difference between being able to pick off a group of raiders, and being surrounded from the get-go. Without a decent perception score, some things may not be obvious to your character, preventing some quests from triggering. After character creation this statistic can be permanantly increased by 1 through use of the green memory module. A temporary boost of 4 points is possible through the use of 2 doses of the mentats drug, but this risks addiction and withdrawl.
Endurance is often picked as the "trash" statistic, but a high endurance can really shine later in the game, especially for melee and unarmed specialists. It's most important role is determining the amount of hit points the player starts with, as well as how many they gain as they progress in levels. It is also used to determine if your character resists additional damage associated with being critically hit, such as falling down or having a limb crippled. A temporary boost of 6 points is possible through the use of 2 doses of the buffout drug, but this risks addiction and withdrawl.
Skills: Speech, Barter
Charisma doesn't determine any secondary characteristics, however it is the only factor taken into account when limiting the number of NPCs that will follow you at a given time. The formula is CHA/2, meaning that a maximum of five NPCs can be used as followers at a given time, note that this limit can NOT be broken with the magnetic personality perk, which usually increases your limit by one. This statistic can be increased by 2, +1 through use of the blue memory module, and +1 by placing the mirrored shades in the ready item slot. A temporary boost of 2 points is possible through the use of 2 doses of the mentats drug, but this risks addiction and withdrawl.
Skills: First aid, Doctor, Science, Repair, Outdoorsman
Intelligence determines two very important things: how many skill points are awarded upon leveling, which is twice your intelligence score, and what dialogue options are available to you. Often times the game will use your intelligence as a backup if you fail a speech check, meaning that you'll be able to talk your way out of (or into) certain situations as long as you're smart enough. An intelligence score that is too low will prevent your character from talking at all, this even prevents you from issuing commands to NPCs. Intelligence can be permanently raised by two, +1 through use of the yellow memory module, and +1 through the completion of the hubologists zeta scan in San Franciso (save first, it can give you +1 int, +1 luck, or simply -2 luck). A temporary boost of 4 points is possible through the use of 2 doses of the mentats drug, but this risks addiction and withdrawl.
Skills: Small guns, Big gun, Energy weapons, Throwing, Unarmed, Melee, Lockpick, Sneak, Steal, Traps
Aside from being the determining statistic for many skills, agility also determines (point for point) how many action points the player will have available each turn during combat for attacking, movment, and other tasks. Agility is used internally to determine if the character succedes in a given act requiring dexterity, such as avoiding a trap they've tripped. Armor class is also effected by agility. There is no memory module to alter agility. A temporary boost of 4 points is possible through the use of 2 doses of the buffout drug, but this risks addiction and withdrawl.
Luck is used to determine how often you score critical hits, as well as how good those critical hits are. For the special Sniper perk, a luck of 10 will cause every hit to become a critical hit. Luck also determines how often special encounters are found while wondering the world map, however it's important to mention that the game doesn't descriminate between "good" and "bad" encounters: while a luck of 10 makes it much more likely to find something great while wondering the map, it also makes it that much more likely you'll find yourself in the middle of the toxic waste dump. An extremely low luck can cause critical failures in combat, which can mean losing all your ammo, destroying your weapon, or even falling down and hurting yourself. Low combat skills can contribute to critical failures, but luck is a primary factor. In the course of the game your luck can be permanently increased by two through use of the hubologist zeta scan in NCR (save first, this scan can either give you +2 luck, or -1 luck).