Eighteen samples of sediments collected from Um Bogma, South Western Sinai, and twelve granite samples collected from Gabal Gattar, North Eastern Desert in Egypt have been investigated. Concentrations of radionuclides in sediment and granite samples were determined by γ-ray spectrometer using HPGe detector with a specially designed shield. The content of uranium is high in sediments and granite samples, and the content of 40K in granite is higher than that in sediments. The absorbed dose rate ranged from 419 to 3908 nGy/h for sediment samples and from 1002 to 1307 nGy/h for granite samples. The representative external hazard indicies (Hex) for sediment and granite samples were estimated. The state of radioactive disequilibrium in the U-series at Um Bogma and Gabal Gattar areas were also studied. The activity ratios between 226Ra/238U for sediment and granite were calculated. Thorium to Uranium concentration ratios (Clark value) was also estimated. The total excess lifetime cancer risk (ELCR) was measured.