Abstract: Employee #1 was using a portable saw that had been set for 2 by 4s to cut some 5/8 in. plywood that was lying across two sawhorses. He made the cut outside the horses without incident and, leaving the cut depth the same, set about cutting another piece of 5/8 in. plywood that was lying on two 4 by 4s on the concrete floor. He was kneeling on the floor and had just started making the cut between the 4 by 4s and himself when the saw kicked back and cut the inside of his right thigh. The saw guard was examined the next day and there were no apparent observed or reported defects. Factors that may have contributed to this accident include an incorrect depth adjustment, cutting inside the material supports rather than outside of them, and the employee's alignment with the cut line. Employee #1 reported that the carpenter to whom he had been assigned had carefully instructed him in the proper method of doing many things--except for using a portable saw. At the time of the accident he had been working as a carpenter's helper for approximately one week.