The objective of this study was to determine and establish for the first time the distribution of mercury species in a tropical lake in order to understand the nature and factors thai influence its biogeochemical cycle. Samples of water, sediments, mussels, and fish muscle tissue collected from Lake Maracaibo were analyzed using a method based on reversed phase high performance liquid chromatography (RP-HPLC) and inductively coupled plasma mass specirometry (ICP-MS) for the separation and determination of mercury species. The effect of physicochemical parameters such as pH, salinity, redox potential, etc., and the nutrients N, P, and S in determining the chemical specialion of these elements were evaluated. The determination of methylmercury and inorganic mercury was perfomed using RP-HPLC and detection by ICP-MS. The species were found in the different environmental samples obtained from Lake Maracaibo.