Lipowitz's metal is widely employed in radiotherapy to create shielding blocks and compensators for X- and gamma-rays. Its effect in modifying radiation beams cannot be evaluated in a simple manner: therefore, in our opinion, an experimental approach to the problem is the most suitable one. Attenuation for Lipowitz's metal and lead was measured in some different geometrical setups, for a 5 MV linac and a 60Co unit. Transmitted fraction vs attenuator thickness curves were obtained. The influence of attenuators on depth-dose curves in a phantom was also evaluated: the results confirm the need to use data obtained in conditions as close as possible to the operative ones, in treatment planning as well as in studying and realizing calculation models.