Temporal and spa hibution of benthic diatoms in the brackish water ponds along Nethravathi estuary was studied for 12 months from Feb. 1998 to Jan. 1999. The benthic diatom population fluctuated between 168 x YO4 to 12858 x lo4 cells/m2. Maximum abundance of diatoms was noticed during May followed by December and September which coincided the periods of low concentration of nutrients in the sediment during late premonsoon and postmonsoon period. About 41 species of diatoms were recorded representing mainly pennate, of which Amphora laevisima, A. ovalis, Cocconies littoralis, Diploneis splendida, Mastogloea dolosa, M. exilli, Nitzschia seriata, N. sigma, Navicula hasta, Pleurosigma angulatum, Trachyneis aspera etc. were dominant. The distribution and variation of benthic diatoms were discussed in relation to temperature, nutrients, pH and texture of the sediment.