[en] In phosphate processing, radium and its decay products are the naturally occurring radioactive materials that are encountered. The radium is present in the original phosphate rock, and passes through without change into the phosphogypsum, which is a by-product of the phosphoric acid industry that is obtained by reacting phosphate rock with sulphuric acid. Because of the weight of sulfuric acid added to the rock to extract the phosphate, the amount of NORM per kilogram of gypsum is less than the amount per kilogram of phosphate rock. In way to contribute for the relative regulation of the handling and use of phosphogypsum as basic input, the determination of the concentration of natural radionuclides was made, as well as the determination of the exhalation rate of ²²²Rn in samples containing different proportions of materials used in the construction industry of Brazil. The work methodology was elaborated based in the needs for a characterization of phosphogypsum. The evaluations of the physical and chemical properties of phosphogypsum were performed through thermal analyses (DTA and TGA); X-rays Fluorescence (XRF) and X-rays Diffraction (XRD). Additional analyses were carried out in order to measure natural radioactivity concentration in different types of samples, as well as the radon exhalation rate. The results showed that the phosphogypsum presents the largest values of concentrations of radionuclides associated to the natural series of ²³²Th. The concentration of ²²⁶ Ra present in the samples varied from 105 to 506 Bq/kg, the ²³²Th from 103 to ²³²Bq/kg and the 40K varied from 205 to 258 Bq/kg. The exhalation rate of ²²²Rn varied from 0.223 to 0.376 Bq/m².min. The final stage of the study evaluated the estimate of the radon concentration inside a typical room with dimensions of (4x4x2.80 m). The results presented values below the reference level adopted by legislation (148 Bq/m³). (author)