In this study, the activity concentrations of some radionuclides in tap water samples of the Eastern Black Sea region of Turkey were measured. The activity concentrations of radionuclides Pb-214, Bi-214, K-40, Ra-226 and Cs-137 were determined using high resolution gamma ray spectrometry. Furthermore, Rn-222 activity concentrations in tap water samples were measured using Liquid Scintillation Counting. The mean specific activities of Pb-214, Bi-214, Ra-226, K-40, Cs-137 and Rn-222 in tap water samples were 6.73, 6, 19.16, 168.57, 5.45 mBq l(-1) and 10.82 Bq l(-1), respectively. These values are comparable with concentrations reported for other countries. The effective doses were determined due to intake of these radionuclides as a consequence of direct consumption of tap water samples. The estimated effective doses were 6.878 x 10(-4) mu Sv y(-1) for Pb-214, 4.800 x 10(-4) mu Sv y(-1) for Bi-214, 3.916 mu Sv y(-1) for Ra-226, 0.763 mu Sv y(-1) for K-40, 0.052 mu Sv y(-1) for Cs-137 and 5.848 mu Sv y(-1) for Rn-222.