[en] NORM stands for 'naturally occurring radioactive material', which is a material that naturally contains one or more radionuclides, mainly, uranium, thorium and potassium-40, and their radioactive decay products, such as radium and radon. An example of this material is the Phosphogypsum (PG), which results from the processing of phosphate ore into phosphoric acid for fertilizer production. In order to support regulation of the reuse of phosphogypsum as a raw material of the Brazilian civil construction industry, a characterization study was performed. The physical and chemical properties of PG and natural gypsum were determinate by evaluating the results of thermal (DTA and TG), X-ray fluorescence (XRF), X-ray diffraction (XRD) and laser granulometric analyses. The radioactivity concentration of each sample was measured by gamma spectrometry analyses. The results of thermal analyses demonstrated that phosphogypsum must be treated (initially heated in an electrical oven at 60 deg. C for 24 hours, then sieved and heated again at 160 deg. C for one hour) to obtain the same mineralogical properties of the gypsum used in the civil construction industry. The X- ray fluorescence analysis showed that PG and natural gypsum are similar with both being composed mainly of S, O, Ca, P and small quantities of trace elements (Ce, Ti, La, Sr, Zr, and Pr). The main crystalline compounds found in PG samples were gypsita (CaSO₄.2H₂O) and in natural gypsum were bassanite (CaSO₄.0.5H₂O). The concentration of Ra-226, Ra-228 and Pb-210 present in PG samples was 467 Bq/kg, 224 Bq/kg and 395 Bq/kg, respectively. The levels of radioactivity in natural gypsum samples were much lower (around 3 Bq/kg). The same behavior was observed for the uranium and thorium content. The results of all the analyses showed that phosphogypsum can be a viable substitute for gypsum, after certain, beneficial processes. (authors)