The rates of denitrification were measured as flows of N₂O in two sites in the Cienaga Grande de Santa Marta as a first step toward the identification of the patterns of this process in tropical coastal lagoons of Colombia. To find out its magnitud, samples of sediment were taken to the lab trials. The rates were related with physical and chemical variables of the sediments and the water column. The rates fluctuated between undetectable and 4305 nrnoles. mˉ² hˉ¹. The maximum flow attributed to bacterial denitrification was 38.8 nmoles.mˉ² hˉ¹. The results showthat denitrification is linked to nitrification of the sedimento It was determined that acetylene blockage assays in anoxic conditions underestimate the rates of denitrification. Apparently nitrification of sediments was blocked by the lack of oxygenand possibly because of the acetylene, which inabilited the production of NO₃ˉ for denitrification. The variations in space and time of denitrification are probably due to factors such as: salinity, porosity of the sediments, content of organic matter and O₂ concentration.