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Radioactivity measurements have been conducted in nine underground phosphate mines in the Egyptian Eastern Desert in order to estimate the occupational radiation exposure of mine workers in those mining sites. Measurements were carried out of airborne radon (Rn-222) and its short-lived decay products (progeny) and thoron (Rn-220) progeny, as well as gamma-radiation from mine walls, ceilings and floors. Comparison of experimental data and theoretical predictions showed partial agreement between these two sets of data. This result is partly attributed to the complex layout of these mines which causes undesirable ventilation conditions, such as recirculation airflow patterns which could not be adequately identified or quantified. The radiation data obtained were used to estimate the Maximum Annual Dose (MAD), and other important occupational radiation exposure variables. These calculations indicate that in eight out of the nine mines surveyed, the MAD exceeded (by a factor of up to 7) the maximum recommended level by ICRP-60. A number of suggestions are made in order to reduce the MAD in the affected mines. (C) 1999 Elsevier Science Ltd. All rights reserved.