In this study, the results of atmospheric radon measurements that were performed for the Amasra underground coal mine in Zonguldak bituminous coal basin (Turkey) are presented. The radon measurements were performed for 40 days between November 2004 and December 2004 using passive nuclear etched track detectors. The radon concentrations vary from a minimum value 49 Bq m(-3) in a site located at +40 m to a maximum value 223 Bq m(-3) in a site located at -100 m. Mean concentration is 117 (Bq m(-3)). This value is well below the action level of 500-1500 Bq m(-3) recommended by the International Commission on Radiological Protection (ICRP) (1993). The mean effective dose value for workers of this mine of 3.4 mu Sv per day was obtained. This result shows that protection against radiological hazards would not be necessary for workers of this mine((2)).