Monster Advancement, LA, and CR

[Prometheus]

I may possibely be witnessing a gulf between v3.0 and v3.5 rules, there seems to be a discrepancy in making a monster encounter with class levels. Supposedly the CR of a single NPC is its class level, I advance Monsters with class levels, and players get monster levels with LA, but this doesn't work out. To add a class level to a monster do I simplt add one to the CR or do I have to add the LA and one?
Example: is a Minotaur (6 HD, LA+2, CR 4) with one added level of Barbarian CR 5 or 7 as far as difficulty, experience, and treasure are concerned?

[Ulzgoroth]

Rules appear in back of the MM, but in short:
If you give them PC class levels that stack well with their innate abilities (barbarian for minotaur, for instance), you add the class levels to the base CR of the monster to obtain the result. NPC or less well-matched levels are messier.

Equip it with an NPC of it's class level's equipment. Loot I'm not sure about.

LA+HD+class levels is ECL, which is the supposed equivalent level for a monstrous PC. This is entirely separate from (and usually higher than) CR,

[Lord Lorac Silvanos]

LA is really only relevant for player characters.

When making an NPC monster with class levels you don't need to worry about the LA.

When you want to advance a monster by giving it class levels you first have to determine whether the class level is associated or non associated.

Your example Minotaur Barbarian would be an example of associated class, while sorcerer would not.

So CR 5, but read more below.

ADDING CLASS LEVELS

If you are advancing a monster by adding player character class levels, decide if the class levels directly improve the monster’s existing capabilities.

When adding class levels to a creature, you should give it typical ability scores appropriate for that class. Most creatures are built using the standard array of ability scores: 11, 11, 11, 10, 10, 10, adjusted by racial modifiers. If you give a creature a PC class use the elite array of ability scores before racial adjustments: 15, 14, 13, 12, 10, 8. Creatures with NPC classes use the nonelite array of 13, 12, 11, 10, 9, 8. T

Associated Class Levels

Class levels that increase a monster’s existing strengths are known as associated class levels. Each associated class level a monster has increases its CR by 1.

Barbarian, fighter, paladin, and ranger are associated classes for a creature that relies on its fighting ability.

Rogue and ranger are associated classes for a creature that relies on stealth to surprise its foes, or on skill use to give itself an advantage.

A spellcasting class is an associated class for a creature that already has the ability to cast spells as a character of the class in question, since the monster’s levels in the spellcasting class stack with its innate spellcasting ability.

Nonassociated Class Levels

If you add a class level that doesn’t directly play to a creature’s strength the class level is considered nonassociated, and things get a little more complicated. Adding a nonassociated class level to a monster increases its CR by 1/2 per level until one of its nonassociated class levels equals its original Hit Dice. At that point, each additional level of the same class or a similar one is considered associated and increases the monster’s CR by 1.

Levels in NPC classes are always treated as nonassociated.

[Zherog]

It depends. There's an ill-defined concept called "associated class" that determines how advancement in a class adds to a monster's CR.

Associated Class Levels

Class levels that increase a monster’s existing strengths are known as associated class levels. Each associated class level a monster has increases its CR by 1.

Barbarian, fighter, paladin, and ranger are associated classes for a creature that relies on its fighting ability.

Rogue and ranger are associated classes for a creature that relies on stealth to surprise its foes, or on skill use to give itself an advantage.

A spellcasting class is an associated class for a creature that already has the ability to cast spells as a character of the class in question, since the monster’s levels in the spellcasting class stack with its innate spellcasting ability.

Nonassociated Class Levels

If you add a class level that doesn’t directly play to a creature’s strength the class level is considered nonassociated, and things get a little more complicated. Adding a nonassociated class level to a monster increases its CR by 1/2 per level until one of its nonassociated class levels equals its original Hit Dice. At that point, each additional level of the same class or a similar one is considered associated and increases the monster’s CR by 1.

Levels in NPC classes are always treated as nonassociated.

edit: le sigh

[Piggy Knowles]

I may possibely be witnessing a gulf between v3.0 and v3.5 rules, there seems to be a discrepancy in making a monster encounter with class levels. Supposedly the CR of a single NPC is its class level, I advance Monsters with class levels, and players get monster levels with LA, but this doesn't work out. To add a class level to a monster do I simplt add one to the CR or do I have to add the LA and one?
Example: is a Minotaur (6 HD, LA+2, CR 4) with one added level of Barbarian CR 5 or 7 as far as difficulty, experience, and treasure are concerned?

Level Adjustment only matters for characters and cohorts, and doesn't effect Challenge Rating. So, a Minotaur with a level of Barbarian (an associated class level) would be CR 5.