Abstract: Four filters for use with a 250 KVP pulsating X-ray machine were constructed to calibrate radiation detection instruments in the energy region below 200 KEV. Approximately monoenergetic beams of 63, 105, 150, and 180 KEV were produced. The spectral distribution was computer suing the formula of Kulenkampff. The energies were found to drop rapidly from the peak values. The average values were checked from absorption curves obtained experimentally and found to deviate from the computed peak values by 10%.