This work presents the results of 137Cs, 40K, 232Th and 238U concentration (Bq kg-1) values in coastal marine sediments collected from 38 sites along the coastline of the island of Margarita, Venezuela. The purpose was to determine baseline values for these radionuclides in surface marine sediments and to detect if there were any anomalously high concentration values. Only three of the 38 sediments analyzed had measurable values above the detection limit of 0.9 Bq kg-1 for 137Cs and the highest only being 1.4 Bq kg-1. While, the concentration (Bq kg-1) ranges for the primordial radionuclides, 40K, 232Th and 238U were as follows: 12.2-211.7, <1.5-9.8 and <4.4-20.7, respectively. These concentration ranges for the primordial radionuclides can be considered as baseline values for surface marine sediments for areas that are considered not polluted by man or contaminated by nature. Finally, the concentration range of 137Cs can also be employed as baseline values, which only seem to have been the result of the atmospheric testing of nuclear weapons in the past. © 2010 Akadémiai Kiadó, Budapest, Hungary.