a b s t r a c t The natural radiation level has been determined for 135 sediment samples from forty-six drinking water purification plants supplied from different sources (Nile River, Ibrahimia Canal and Bahr Yousif Canal) aiming to evaluate the radiation hazard. The concentration of natural radionuclides (226 Ra, 232 Th and 40 K) has been investigated by using gamma spec-trometry (NaI (Tl) 3 00 Â 3 00) detector. The results showed that the concentrations of average activity in the sediment samples collected from Nile River, Ibrahimia Canal and Bahr Yousif Canal are (29 AE 2, 30 AE 2 and 240 AE 8 Bq kg À1), (47 AE 3, 46 AE 8 and 258 AE 12 Bq kg À1) and (28 AE 2, 27 AE 3 and 219 AE 18 Bq kg À1) for 226 Ra, 232 Th and 40 K, respectively. The dis-tributions of average activity concentrations of samples under investigation are within the world values although some extreme values have been determined. Radiological hazard effects such as: absorbed dose rate (D), outdoor and indoor annual effective dose equiva-lent (AEDE), radium equivalent activities (Ra eq), hazard indices (H ex and H in), gamma index (I g), excess lifetime cancer risk (ELCR) and annual gonadal dose equivalent (AGDE) for the corresponding samples were also estimated.