PURPOSE: To provide a silica-filled rubber compound comprising a rubber, a silica-containing filler, a crosslinking agent, a rubber auxiliary and a specific mercaptoalkyl silyl ether and a specific guanidine which is excellent in modulus of elasticity, abrasion resistance or the like and useful for tires, hoses or the like.

CONSTITUTION: A desired composition comprises (A) at least one rubber; (B) a crosslinking agent; (C) a silica-containing filler; optionally (D) other rubber auxiliaries; and (E) at least one compound of formula I (wherein R1 is H or a 1-8C alkyl, preferably a 1-4C alkyl; R2 and R3 are each H, a 1-12C, preferably 1-6C alkyl or the like; R4 to R6 are each a 1-18C, preferably 1-6C alkyl, alkenyl or the like; n is an integer of 0-8, preferably 0-4) or of formula II (wherein R7 to R9 are each H, a 1-12C, preferably 1-6C alkyl or the like), the compound of formula I being used in an amount of 0.1-15 (wt.)% and the compound of formula II being used in an amount of 0.05-5%, based on the amount of the rubber used. As the compound of formula I is preferred a compound of formula III or the like, and as the compound of formula II is preferred a compound of formula IV or the like.