Influence of dissolved organic carbon (DOC) on the quantitative estimation of Pu-239+240 in the groundwater was investigated. Impact of DOC in the range of 5-30 ppm was studied in solutions which were directly taken from different wells, whereas to conduct the experiment at the elevated level of DOC, i.e. in the range of 27-60 ppm, groundwater was spiked with stock solution of humic acid (HA), a high molecular weight organic compound. Samples with varying concentrations of DOC were artificially contaminated with a pre-calibrated solution of Pu-239+240 in the laboratory in the range of 200 mu Bq-17 Bq l(-1), and the pH was controlled at 7.4. Quantitative estimation of plutonium was carried out by pre-concentrating it with Fe(OH)(3). This purified plutonium from Ca2+, Mg2+ and amphoteric elements. The percentage recovery of Pu-239+240 was 90-92% in the solution having DOC congruent to 10 ppm, whereas in samples with DOC in the range of 10-60 ppm, the recovery was 42-43%. Therefore, to improve the recovery of plutonium in the case of the elevated level of DOC, a modified procedure for its quantitative estimation was adopted. In this procedure, after filtration the samples were refluxed with cone. HNO3 and H2O2 to destroy the DOC before pre-concentrating Pu with Fe(OH)(3). By this modified procedure, the average recovery of plutonium at high concentrations of DOC was improved to 90-95%.