Natural ( 2 3 8 U and 2 3 2 Th series, 4 0 K) and artificial ( 1 3 7 Cs) radioactivity levels in the sediments of Algiers bay were measured using gamma-ray spectrometry. Concentrations (Bq kg - 1 , dry weight) have been observed to range from 10.8 to 25.0 for 2 3 8 U, from 6.5 to 31.7 for 2 3 2 Th, from 55.9 to 607.4 for 4 0 K and from 0.95 to 9.5 for 1 3 7 Cs. These values are discussed in terms of the facies type of the sea bottom.