Groundwater dissolves radioactive minerals like uranium, radium, radon and polonium during its ow. 226 Ra, 222 Rn, and 210 Po are the decay products of the 238 U series which causes ingestion dose to human being. The activity of these radionuclides was studied in groundwater samples collected from Chamarajanagar district, Karnataka, India. 226 Ra, 222 Rn and 210 Po concentration in bore well water samples were varied from 2.18 to 96.42mBql − 1 , 0.94 to 26.95Bql − 1 , 0.72 to 6.33mBql − 1 respectively. The average ingestion dose due to 226 Ra, 222 Rn and 210 Po were 6.41, 11.60 and 2.51µSvy − 1 respectively.