Samples of marine surface sediments of different grain sizes collected in Gokova. a small bay on the Aegean Turkish Coast, have been examined to measure alpha- and gamma-radioactivity. The purpose of this research is to define a baseline study of man-made radionuclides on sediments along Gokova Bay, using a combination of direct gamma-spectrometry, radiochemical separation and alpha spectrometry. The analysis of these samples revealed measurable quantities of some artificial radionuclides namely: Pu239+240 (from 0.13+/-0.017 to 0.85+/-0.15 Bq.kg(-1)). Cs-137, Am-241, and Pu-238 were identified at a very low level. Concentration ratios of Pu-238 to Pu239+240 obtained seem to confirm that this artificial radioactivity is due mainly to Chernobyl accident.