Most Data On radium protection are based on the absorption coefficients obtained with narrow collimated beams and on the application of the “inverse-square” law. Yet, in the majority of protection problems we are dealing with radiation that is not limited to a small cross section and with conditions where the scattered radiation from neighboring objects contributes considerably to the dose received by the radium workers. In thisstudy we have compared the transmission of gamma radiation through lead for narrow and broad beams. Experiments were arranged also to determine the validity of the “inverse-square” law as applied to radium protection. Finally, a study was made of the protection obtained with lead shields of the type used while handling radium. Apparatus And Experimental Procedure The characteristics of the three types of ionization chambers used in this investigation are shown in Table I. The spherical chamber, SX-11, was used for all the measurements2 after preliminary tests had shown that the dif...