The influence of landscape on nutrient concentrations and yields was analyzed in a tropical catchment.  Spatial and temporal variation in nitrate, SRP and total P were determined at 15 sites located along the river mainstem and tributaries of the Guare River in northern Venezuela.  Landuse and slope above each sampling site were derived from a GIS for the catchment.  Higher nitrate concentrations and yields were recorded at upper sites, and values decreased in the downstream direction along the river mainstem.  This trend is related to higher slopes and a greater proportion of agricultural lands in the upper watershed, and dense algal mats in the lower reaches.  Nitrate showed higher values during periods of high discharge, suggesting that nitrate is transported primarily along surface flowpaths. SRP represented between 60 and 80% of total P.  Phosphorus concentrations were homogeneous along the river mainstem and showed little seasonal variation, while yields were higher in the upper basin.  Multiple regression identified slope, runoff, and agriculture as primary predictors of nitrate and phosphorus across the watershed, indicating that both natural and anthropogenic landscape characteristics have a strong influence on nutrient levels in the Guare catchment.