Radioactivity of naturally occurring (226Ra, 232Th and 40K) and anthropogenic (137Cs) radioactive nuclides was measured in 29 potable ground and surface water samples of Punjab, Pakistan. The results showed average activity concentrations for 226Ra, 232Th, 40K and 137Cs as 1.09, 0.55, 16.17 and 0.40 Bql−1, respectively. 137Cs was detected in only a few samples. The obtained results showed that, in general, activity concentrations of radionuclides (232Th and 137Cs) in drinking water samples did not exceed WHO recommendations. 226Ra in the majority of samples exceeded WHO drinking water guidelines. The estimated committed effective dose due to intake of the water for three age-groups considered (<1 y, 2–7 y and ≥17 y) was below the ICRP permissible limit (0.1 mSvy−1) except for 226Ra and 40K.