As insights from tolerance responses of native microflora are useful in deciphering their involvement in biogeochemical cycling of heavy metals, we enumerated mercury resistant bacteria (MRB) using sea water nutrient agar medium amended with 10 ppm Hg from oceanic and coastal waters of the Bay of Bengal (BOB) during the summer monsoon (July–August 2001) period. MRB were present in all samples and, intriguingly, the MRB percent based on total viable counts (TVC) increased significantly (r = 0.86; P less than 0.001; df = 44) with depth. On an average, MRB contributed to over 20% of TVC on the surface, 12% at 100 m, 35% at 500 m and a staggering 49% at 1000 m. The fact that a major portion of the natural, culturable bacterial flora was mercury-resistant from the offshore regions of the BOB points to the global nature of mercury pollution. The higher percentages of MRB in the offshore waters of the BOB might signify the already prevalent adverse impact of heavy metals on the metabolic performance of heterotrophic microflora.