Abstract: The background radioactivity in sediment samples collected mainly from the edge of streams and rivers during dry season in Akoko in Ondo state southwestern Nigeria have been determined using a gamma spectrometry technique in this study. The activity concentration measured in various sediment samples was found to vary from 142.57�5.14 to 839.28�20.45 Bq kg^�1 for ⁴⁰K from 9.40�0.41 to 52.71�0.97 Bq kg ¹ for ²²⁶Ra and from 24.87�1.29 to 301.14�3.60 Bq kg ¹ for ²³²Th. No artificial radionuclide was detected in the samples. The radiological effect of the natural radioactivity in the sediment samples was assessed using the radium equivalent activity and the absorbed dose terms. The calculated mean values of radium equivalent activity and absorbed dose rate in air obtained are 140.54 Bq kg ¹ and 68.42 nGy h^�1 respectively and the effective dose posed to humans when the sediments are exposed was obtained to be 0.08 mSv y ¹.