Abstract: At approximately 10:20 a.m. on December 1, 1988, Employee #1 and a coworker were removing the wear pads from the boom of a Grove aerial lift so that the boom section could be removed and a hydraulic leak repaired. The 570 lb boom section was approximately 7 ft off the floor. The aerial lift basket had been completely disconnected from the end of the aerial lift boom and was resting on two Economy Hijacker mobile ladder stands that were approximately 8 ft above the floor. The casters on the ladder stands had not been locked nor were they chocked to prevent movement. The coworker who had helped Employee #1 remove the two top wear pads then told him to remove the remaining two pads at the bottom of the boom while he went out to park another piece of equipment. The coworker stated that before he left he saw Employee #1 with a hand winch. Employee #1 had removed the wear pad on the inside of the boom but due to the height of the boom had encountered difficulty in shifting it so that he could remove the other wear pad. He had apparently climbed up the northwest mobile ladder stand to shift the boom and free the wear pad when the ladder stands began to move. This caused the aerial lift basket to fall 8 ft to the concrete floor, which in turn caused Employee #1 to fall backward off the mobile ladder stand and drop approximately 4 ft to the floor. A coworker found the employee with his right leg wedged between the fourth and fifth steps of the mobile ladder stand, and his head resting on the floor. Employee #1 died at approximately 2:40 p.m. that afternoon from head injuries.