The aim of this study is to investigate the contents of essential and toxic trace element by the energy-dispersive X-ray fluorescence spectrometry (EDXRF) in seaweed (Viva lactuca) from collected eight different regions of Istanbul (Turkey) in the years of 2006 and 2007. It has been analyzed by the samples using two annular radioactive sources and an Ultra-LEGe detector. A radioisotope excited X-ray fluorescence analysis using the method of multiple standard additions was applied for the elemental analysis of seaweed samples. In this study, the metal concentrations in the seaweed samples vary within 0.8-1.8% and 1.1-2.1% for Cl, 0.6-2.3% and 0.2-3.4% for K, 0.9-2.7% and 0.4-2.7% for Ca, 0.2-1.0% and 0.2-0.3% for Ti, 0.7-2.1% and 0.7-2.3% for Fe, 0.05-0.1% and 0.04-0.1% for Br, 0.3-0.6% and 0.3-0.4% for Sr, 0.1-0.2% and 0.1-0.2% for I, and 0.09-0.3% and 0.09-0.1% for Ba in the years of 2006 and 2007, respectively. The results demonstrated that these seaweeds contain some essential element, but no toxic element.