-2 Dexterity, +2 Constitution.
Medium: As Medium creatures, duergar have no special bonuses or penalties due to their size.
Speed: Duergar base land speed is 20 feet. However, duergar can move at this speed even when wearing medium or heavy armor or when carrying a medium or heavy load (unlike other creatures, whose speed is reduced in such situations).
Darkvision: Duergar can see in the dark up to 60 feet. Darkvision is black and white only, but it is otherwise like normal sight, and duergar can function just fine with no light at all.
Weapon Familiarity: Duergar may treat dwarven waraxes and dwarven urgroshes as martial weapons, rather than exotic weapons.
Stability: A duergar gains a +4 bonus on ability checks made to resist being bull rushed or tripped when standing on the ground (but not when climbing, flying, riding, or otherwise not standing firmly on the ground).
+2 racial bonus on saving throws against poison.
+2 racial bonus on saving throws against spells and spell-like effects.
+1 racial bonus on attack rolls against humanoids of the reptilian subtype (including kobolds and lizardfolk) and dragons (including half-dragons).
+4 dodge bonus to Armor Class against dragons.
+2 racial bonus on Appraise checks that are related to stone or metal items.
+2 racial bonus on Knowledge (architecture and engineering), Knowledge (dungeoneering), and Profession (miner) checks.