The surface hydrophobicities of fungal spores from the entomopathogenic generaBeauveria,Metarhizium, andTolypocladiumwere quantitatively measured and compared using a novel assay employing salt-mediated aggregation and sedimentation (SAS). Spores with greater hydrophobicities were easily identified by their aggregation and sedimentation out of suspension at faster rates under lower salt concentrations. Of the three ammonium salts investigated for their salting-out potentials, ammonium sulfate gave the most pronounced effect, closely followed by ammonium chloride, and then ammonium acetate. Using the SAS assay, spores exhibited more pronounced hydrophobic properties at pH 5.8 than at higher pH values of 6.8 and 7.8. The effects of temperature and spore concentration upon the SAS assay were also investigated, with greater spore sedimentation occurring at elevated temperature. By plotting SAS values for two ammonium salt concentrations (0.01 and 0.1 M) in a coordinate system, it was possible to differentiate the hydrophobicities of all five spore isolates, clearly demonstrating the superiority of SAS over an existing phase-exclusion assay. The significance and potential of the SAS assay are also discussed.Key words: fungal spores, hydrophobicity, microassay, SAS, salting out, microbial insecticides.