Abstract: Employees #1 and #2 were installing scissor roof trusses. The crane had been poorly positioned and could not raise the plywood sheathed end truss into place. Truss #1, placed approximately 23 in. from the end wall, was nailed to the front and rear walls and a brace (two overlapping 2 by 6's) was attached to the center vertical web member and the floor. Truss #2 was also attached to the front and rear walls, and a top chord lateral brace, consisting of 3/4 in. thick plywood 3 in. wide by 25 1/2 in. long, was nailed to truss #1 and #2 near the peak. Employee #1 was standing on the truss and Employee #2 was probably standing on the floor-to-truss brace. While trusses #3 and #4 were being unhooked from the crane, the floor-to-truss brace fractured and the plywood strip bracing the top chord broke away from the nails. Employee #1 and trusses #1 and #2 fell approximately 31 ft from the side of the building to a soft backfilled area. Employee #2 fell approximately 12 ft to the second floor level. Employee #1 suffered from a fractured thoracic vertebra and a fractured wrist. Employee #2 was transported to the hospital with minor injuries. Causal factors included: failure to install the end wall truss; failure to install temporary lateral bracing of the bottom chord; inadequate temporary lateral bracing of the top chord plane (they should have used at least 2 by 4s), and failure to install a lateral brace in the opposing direction from that of the floor-to truss-brace. None of the employees had received hazard recognition training or training in the Truss Plate Institute's standards recommendations. None of the employees wore hard hats or were provided with or wore safety belts and lanyards.