Bottom sediments reflect in general the relative contamination of a sea area. Therefore, a great deal of monitoring work has been dedicated to the analysis of bottom sediments. Izmir Bay is a very important pollution centre in Turkish Aegean coast region due to a densely populated community, industrial complex and maritime transportation, and there are many streams flowing into the bay that pass through a number of industrial and agricultural areas. It had received the majority of domestic and industrial wastewaters until the wastewater treatment plant was constructed. It is well known that sediments play an important role as reservoirs of a fraction of the pollution in aquatic systems. Therefore, sediment samples were collected monthly from three stations which are located in the inner part of the bay during the period January to December 2003. Temporal variations and seasonal changes on their Po-210 and Pb-210 contents were examined, and the activity concentrations of Po-210 and Pb-210 were found to vary from 43 +/- 6 to 132 +/- 12 and 27 +/- 5 to 91 +/- 9 Bq kg (-aEuro parts per thousand 1) dry wt, respectively. The highest values of those natural radionuclides were measured at KarAYA +/- yaka Station because of the current systems of the bay. Seasonally, the Pb-210 levels were found to increase during the winter time for all the stations.