Applicability of polyaniline (PANI) has been investigated for the preconcentration and speciation of inorganic mercury (Hg 2+ ) and methyl mercury (CH 3 Hg + ) in various waters (ground, lake and sea waters). Preliminary experiments (batch) with powdered PANI for the quantitative removal of both Hg 2+ and CH 3 Hg + showed that the retention of Hg 2+ was almost independent of pH while a pH dependent trend from pH 1 to 12 was seen for CH 3 Hg + with maximum retention at pH>5. Time dependence batch studies showed that a contact time of 10min was sufficient to reach equilibrium. The K d values were found to be ∼8×10 4 and ∼7×10 3 for Hg 2+ and CH 3 Hg + , respectively.Subsequently column experiments were carried out with PANI and the separation of the species was carried out by selective and sequential elution with 0.3% HCl for CH 3 Hg + and 0.3% HCl–0.02% thiourea for Hg 2+ . This was then followed by further pre-concentration of mercury on a gold trap and its determination by CVAAS. The uptake efficiency studies showed that the PANI column was able to accumulate up to 100mgHg 2+ /g and 2.5mgCH 3 Hg + /g. This method allows both preconcentration and speciation of mercury with preconcentration factors around 120 and 60 for Hg 2+ and CH 3 Hg + , respectively. The interfering effects of various foreign substances on the retention of mercury were investigated.