This work was ini tia ted by the large discrepancy in published values of the backscatter factor (BSF) as function of the half value layer (HVL) that exists in a new code of practice (IAEA, 1987) compared to the earlier, general ly used code (BJR, 1983). Change to the IAEA-code changes reported values of absorbed dose with up to 10%. These deviations apply for X-rays with HVL < 8 mm Al.