The friction coefficient of short-fiber-reinforced rubber (SFRR) was examined under dry and wet conditions. When the unfilled rubber is rubbed against a dry glass disk, the friction coefficient is higher than that of the SFRR and decreases as contact pressure increases. On the other hand, the friction coefficient for the SFRR is relatively low, and decreases slightly with the increase of contact pressure. When the unfilled rubber is rubbed against a silicone oil-lubricated glass disk, the friction coefficient is lower than that in a dry condition, and decreases with increasing sliding speed to reach a minimum value. After that, it increases slightly with the increment of the sliding speed at the sliding speed range examined. The friction coefficient of the SFRR on the wet surfaces is lower than that of the unfilled rubber at low sliding speeds. With an increase in speed, the friction coefficient initially decreases, and then reaches a minimum value. After that, it increases with the increment of sliding speed. The minimum for the unfilled rubber and the SFRRs shifts toward lower sliding speeds when the contact pressure is increased. Therefore, under the condition of mixed lubrication at low speeds, the friction coefficient at low contact pressure is higher than that at high contact pressure. This trend is distinguishable as the fiber content of the SFRR is increased. The phenomena at high contact pressures arise from the reduction of effective surface roughness, as the unfilled rubber deforms and the SFRRs deflect because of the applied load. (C) 2004 Wiley Periodicals, Inc.