A crosshead piston bearing assembly is disclosed. The piston bearing comprises a part-cylindrical upper bearing segment, or slipper, and a pair of spaced part-cylindrical lower bearing segments, or ears, engageable with the upper segment to form a pair of spaced continuous circular bearing surfaces and having an anti-rotation projection on either the slipper or the piston bore. The slipper has an arcuate extent of less than 180.degree. to facilitate replacement of the slipper. The ears have a complementary arcuate extent. The slipper includes axially-spaced notches formed in the ends of the slipper to engage the ears to prevent the ears from moving inwardly into contact with the connecting rod.