Reactive silicate and salinity values in surface and bottom waters of Rushikulya estuary showed well marked seasonal fluctuations. The annual cycle of silicate exhibited unimodal oscillation with peaks and falls occurring during monsoon and premonsoon seasons respectively. The concentration of silicate (mu-g-at.l-1) in surface water ranged from 4.12-191.86, while in bottom water it varied between 4.37 and 195.27. Significant inverse relationship between salinity and silicate indicated that freshwater influx is the principal source of silicate for this environment.