A tungsten coil (150 W, 15 V) was used as the atomizer for the proposed Flow Injection Vapor Generation Atomic Absorption Spectrometry (FI-VGAAS) system to determine inorganic mercury and total mercury concentrations. In the proposed method inorganic mercury was measured when the W-coil is at room temperature and total mercury was measured when the W-coil temperature was set to 500 degrees C. The organic mercury concentration was calculated by subtracting the inorganic mercury concentration from the total mercury concentration. The calibration graphs were linear up to 100 ng ml(-1). Limit of detection (LOD) values for inorganic mercury and methyl mercury were 0.60 ng ml(-1) and 0.89 ng ml(-1) respectively. The precision of the method in terms of RSD was between 2-3%, and the sampling frequency was 100 h(-1). In order to validate the proposed method, known concentrations of methyl mercury and inorganic mercury were spiked into deionized water and tap water samples. Certified reference materials (CRM) IAEA-085 and NRC DOLT-3 were analyzed after microwave assisted extraction with 6.0 mol l(-1) HCl solutions. Both inorganic mercury and methyl mercury concentrations were in agreement with the certified values.