This study assesses the level of background radiation for Canakkale province of northwestern Turkey. Radon concentrations in indoor air were determined using CR-39 nuclear track detectors and Rn-222 activity was found to be 167 Bq m (-aEuro parts per thousand 3) (equivalent to an annual effective dose of 4.2 mSv). Measurements of outdoor gamma radiation (of terrestrial and cosmic origin) in air were performed using plastic scintillators, and the average absorbed gamma dose rate was found to be 66.4 nGy h (-aEuro parts per thousand 1) (corresponding to an annual effective dose of 81.4 mu Sv). The radionuclide activity concentrations in soil samples collected from the study area were measured through gamma-ray spectrometry, and the average activities were determined as 94.55, 110.4, and 1,273 Bq kg (-aEuro parts per thousand 1) for the natural radionuclides U-238, Th-232, and K-40, respectively, and 19.39 Bq kg (-aEuro parts per thousand 1) for the fission product Cs-137. The natural radioactivity sources resulted in an annual effective dose of 184 mu Sv. The radioactivity levels of drinking water samples were measured as 0.0599 Bq l (-aEuro parts per thousand 1) for gross-alpha activity and 0.0841 Bq l (-aEuro parts per thousand 1) for gross-beta activity using a low-background counting technique (equivalent to an annual effective dose of 12.25 mu Sv). The results of this study show that the activity levels of radon in air, radionuclides in soil, and alpha activities in drinking water are higher compared to the data available for other Turkish cities and the world averages. On the other hand, the outdoor gamma dose rates in air and beta activities in drinking water are within natural limits.