The toxic effects of an organophosphate nematicide (Fosthiazate) and a benzenoid fungicide (Metalaxyl-M) have been evaluated by the use of the fresh water algae P. subcapitata. The effects of copper (Cu +2 ), an ingredient of many fungicidal mixtures, have also been assessed on the same organism, as well as the interactive effects of binary mixtures of the three aforementioned agrochemicals. Finally, leachates containing fosthiazate in two different concentrations have been tested on the bioluminescent bacterium Vibrio fischeri. The interactive effects of the binary mixtures were additive in most cases, while fosthiazate leachates exhibited low, dose-related toxicities.