Half value layer(radiation energy) of $90^{circ}$ scattered radiation from various radiation shielding materials was measured at 1 m distance from the central ray of the primary beam. Scattered radiation was measured from 100 to 200 kVp for 0-2.0mm Cu+1.0mm Al added filter in the primary beam for a deep therapeutic unit, the obtained results were as follows: 1. The ratio of scattered radiation to primary radiation was increased by using lighter filter. 2. The ratio of scattered radiation to primary radiation was decreased by using heavier filter. 3. The ratio of scattered radiation to primary radiation was independent of tube voltage. 4. The scattered radiation of high energy was produced, when the effective atomic number and density of shielding material were high.