Many studies have shown an association between operating heavy construction equipment and symptoms of musculoskeletal disorders (MSDs), little research has been performed that systematically characterizes the exposure of operating engineers to ergonomic hazards. This study evaluated: 1. vibration at the seat/operator interface, 2. transmissibility of vibration in the Z-axis, 3. psychophysical ratings of vibration level and vibration discomfort, and 4. postural requirements of the job. Results indicate that the digging operation had higher levels of total weighted acceleration than high- or low-idling conditions. Transmissibility data showed that the seat amplified vibration, particularly in the lower frequencies. Seats demonstrated that they may not be sufficient in protecting operators from longterm effects of vibration exposure. High positive correlation was found among subjective ratings (vibration discomfort and vibration level), but moderate positive correlation was found between subjective ratings and quantitative vibration levels.