[en] This report presents the results of a study carried out to estimate the annual effective dose equivalent contribution from phospho-gypsum plaster-board if it were used as an internal lining in buildings. The study considered four sources of radiation exposure that would arise in such use, such as inhalation of ²²²Rn and its daughters, inhalation of phospho-gypsum dust and exposure to beta and gamma radiation. Measurements of the ²²6Ra content and ²²²Rn exhalation rate were made for a number of samples of phospho-gypsum plaster-board, and the behaviour of ²²²Rn and its daughters in a typical building was modelled. The results of the study suggest that, for building ventilation rates greater than approximately 0.5 air changes per hour, the contribution to the total annual effective dose equivalent from inhalation of radon (²²²Rn) and its daughters (²¹⁸Po, ²¹⁴Pb, ²¹⁴Po) exhaled from the phospho-gypsum plaster-board should be well below the recommended limit of 1 milli-Sievert for members of the public. The total annual effective dose equivalent from all these sources should be less than 0.6 milli-Sieverts, provided reasonable work practices are observed during installation of the phospho-gypsum plaster-board and the ventilation rate is kept above approximately 0.5 air changes per hour. 31 refs., 12 tabs., 5 figs