[en] An important parameter commonly used to describe the behavior of a porous material is its porosity that is of great interest in several areas of the engineering and applied physics. In this work, the total porosity of three different amorphous materials were measured: TRe soil (eutrophic dark red soil) extracted from an area of forest preservation at the Uhl Campus, Laender,PR; Berea sandstone rock, supplied by CENPES/PETROBRAS and three kinds of porous ceramic of the type Al₂O₃-SiC, named C-60, C-75 and C-90 samples, used in the metallurgical industry as filter of liquid metals, made by the Material Engineering Department of USP, SP. The measurement of the porosity samples was carried out employing the gamma-ray transmission method. It has the advantage of being accurate, fast and allowing the porosity results to be shown point by point in millimetre scale (or less) without intervening in the physical integrity of the sample. The results obtained with the gamma-ray transmission method were compared with the measurements with conventional Archimedes method. The gamma-ray transmission system consisted of a ²⁴¹Am (59.6 keV) radiation source (300 mCi), collimated with a cylindrical lead collimator of 0.002 m diameter. Radiation was detected with a 2x2'' NaI(Tl) crystal, standard gamma spectrometric electronics chain connected to a multichannel and a XYZ micrometric table for the samples positioning. Some results include the following (sample, total porosity): Berea sandstone rock: 29.68; C-60: 89.74; C-75: 90-68; and C-90: 71.14